perception and understanding of how local exhaust ventilation

Health and Safety Executive

Perception and understanding of how local exhaust ventilation (LEV) works and how effective it is: Phase 2

Prepared by the Health and Safety Laboratory for the Health and Safety Executive 2011

RR836 Research Report


Perception and understanding of how local exhaust ventilation (LEV) works and how effective it is: Phase 2

Daniel A Greaves Health and Safety Laboratory Harpur Hill Buxton Derbyshire SK17 9JN

Background: Health and Safety Executive (HSE) inspectors had anecdotal evidence that employers and employees had misperceptions and overconfidence in LEV systems. Therefore, HSE commissioned the Health and Safety Laboratory (HSL) to gain insight into these users’ current understanding and perceptions relating to different types of LEV systems as well as compare and contrast the results of these two groups.

Methodology: A HSL researcher devised a bespoke methodology using a qualitative approach that consisted of semi-structured questionnaires, a series of 2D line drawings and cut-out LEV hood pictures. These were applied together in face-to-face interviews with a purposive sample of employers and employees from the manufacturing sector who owned/used LEV systems within the UK.

Results: Participants had an adequate understanding of the basic principles of LEV systems. However, many had limited training on LEV and most of their information came from manufacturers, suppliers and installers. There were many misperceptions and overconfidence in the use and effectiveness of LEV that were found specifically in relation to the capture zone (area of air suction around the hood).

Conclusion: Although employers and employees knew the basics of LEV use and operation there was a cluster of misperceptions and overconfidence in relation to the interpretation of the capture zone. Therefore, the results could be used by HSE as part of its wider communication strategy and in order to dispel misperceptions and overconfidence amongst employers and employees perhaps by showing them how a capture zone works and how contaminants interact with it.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the author alone and do not necessarily reflect HSE policy.

HSE Books

© Crown copyright 2011

First published 2011

You may reuse this information (not including logos) free of charge in any format or medium, under the terms of the Open Government Licence. To view the licence visit www.nationalarchives.gov.uk/doc/open-governmentlicence/, write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email [email protected].

Some images and illustrations may not be owned by the Crown so cannot be reproduced without permission of the copyright owner. Enquiries should be sent to [email protected].

ACKNOWLEDGEMENTS

The author would like to thank all the participants who were interviewed for this piece of research, and HSL colleagues, John Saunders, Dominic Pocock, Simon Bates, Chrysanthi Lekka, Helen Beers, Roxane Gervais and Julie Bell for their expertise and advice.

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CONTENTS

1 INTRODUCTION......................................................................................... 1 1.1 Background ............................................................................................. 1 1.2 Aims and objectives................................................................................. 1

2 DATA COLLECTION AND ANALYSIS ...................................................... 2 2.1 Sample .................................................................................................... 2 2.2 Data collection tools................................................................................. 3 2.3 Procedure and tools test.......................................................................... 4 2.4 Data collection ......................................................................................... 4 2.5 Data analysis ........................................................................................... 5

3 FINDINGS................................................................................................... 7 3.1 Summary demographic information......................................................... 7 3.2 Qualitative analysis.................................................................................. 7 3.3 Expert rating of 2D line drawings........................................................... 15 3.4 Summary of key findings ....................................................................... 17

4 DISCUSSION............................................................................................ 21

5 CONCLUSION .......................................................................................... 24

6 REFERENCES.......................................................................................... 25

7 APPENDICES........................................................................................... 26

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EXECUTIVE SUMMARY

Local Exhaust Ventilation (LEV) is one of the principal methods used to control exposure to airborne contaminants that can cause work-related ill health, including respiratory disease. However, HSE inspectors have found that some LEV systems do not work effectively for a number of reasons. There is anecdotal evidence that poor design, application and performance along with misperceptions and overconfidence amongst employers and employees (that LEV systems perform better than they are actually able to) about how LEV hoods control exposure to airborne contaminants, are responsible for this apparent ineffectiveness.

HSE want to engage this audience group in order to counter any misperceptions and overconfidence. To do this, HSE required insight into employers’ and employees’ current understanding and perceptions of LEV use and effectiveness. HSE commissioned the Health and Safety Laboratory (HSL) to conduct a study to collect evidence as to employers’ and employees’ perceptions of LEV. HSL devised a methodology using a qualitative approach that consisted of semi-structured questionnaires and a set of 2D line drawings that were used in combination to determine the factors relating to current perceptions of LEV use and effectiveness from a purposive sample of UK businesses.

Aims

The aim of this study was to collect data on employers’ and employees’ (or users) perceptions and understanding of how different types of LEV systems1 work, and how they should be used to effectively control exposure to airborne contaminants.

Objectives

The specific objectives of the work were:

• To obtain information from two distinct groups (employers and employees) on their perceptions of the use and effectiveness of LEV systems;

• To compare and contrast employer and employee results of perceptions relating to use and effectiveness of LEV;

Main Findings

• Participants had a good understanding of the principles of LEV, components, contaminant characteristics as well as the benefits and drawbacks;

• The main sources of information and advice on LEV were provided by manufacturers, suppliers and installers;

• Generally there was a good level of understanding of appropriate use of RPE/PPE and possible repositioning of LEV;

• Participants had received little or no training on the use and effectiveness of LEV;

• There were many similarities between employer and employee responses overall;

1 Enclosure, Capturing and Receiving hoods

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• Many misperceptions and overconfidence (that LEV systems perform better than they are actually able to) in the use and effectiveness of LEV were found in relation to the capture zone (area of air suction around the LEV hood);

• In general, misperceptions included the capture zone: being stronger in the centre and weaker at the sides; following the line/angle of the hood (and tapering inwards or outwards further away from the hood); being based on the hood shape and size; being the wrong shape i.e. cone/arc or column shaped (or both); recapturing contaminant and affecting the gas shield if positioned too close;

• There is an overconfidence in the capture zone, which included assuming it: was larger than it is; had a wide range of capture; was similar to a vacuum cleaner, chimney or cooker hood; was 100% effective and having no perceived drawbacks;

• A minority of participants demonstrated correct perceptions and level of confidence in LEV that was thought to be informed by either a science or engineering background as well as various HSE LEV guidance/information.

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1 INTRODUCTION

1.1 BACKGROUND

Local Exhaust Ventilation (LEV) is one of the principal methods used to control exposure to airborne contaminants that can cause work-related ill health, including respiratory disease. However, HSE inspectors have found that some LEV systems do not work effectively for a number of reasons. The HSE LEV project team has anecdotal evidence that poor design, application and performance along with misperceptions and overconfidence (that LEV systems perform better than they are actually able to) amongst employers and employees as to how LEV hoods control exposure to airborne contaminants, are responsible for this apparent ineffectiveness.

The Health and Safety Executive (HSE) has produced new LEV guidance for three audiences (suppliers, employers and employees). However, there is a need to communicate the key guidance messages in a form, and in a way, to which the audiences are receptive. To inform their larger communication strategy with these audiences, HSE requires a greater insight into the audience’s current understanding and perception of LEV system use and effectiveness. The results of this study can be used to inform and contribute to HSE’s wider communication strategy on LEV.

HSL was commissioned by HSE to conduct a study to investigate employers’ and employees’ perceptions and understanding of LEV in relation to its use and effectiveness, following on from the earlier scoping study (Greaves & Holroyd, 2009).

1.2 AIMS AND OBJECTIVES

The aim of this study was to collect data on employers’ and employees’ (or users) perceptions and understanding of how different types of LEV systems2 work, and how they should be used to effectively control exposure to airborne contaminants. The results of this study can be used to inform and contribute to HSE’s wider communication strategy on LEV.

Objectives

The specific objectives of the work were:

• To obtain information from two distinct groups (employers and employees) on their perceptions of the use and effectiveness of LEV systems;

• To compare and contrast employer and employee results of perceptions relating to effectiveness and use of LEV;

2 Enclosure, capturing and receiving hoods 1

2 DATA COLLECTION AND ANALYSIS

2.1 SAMPLE

A target sample size of 20 employers and 40 employees from the UK was agreed between HSE Social Science Unit (SSU), the HSE customer and HSL. The sample size was established as appropriate for collecting sufficient information to carry out a qualitative analysis. The study was also subject to HSE Survey Control, which works to minimise the impact of survey work on UK business.

• ‘Employers’ – were defined as one person from each company who had ‘owner’ knowledge of the LEV system. Specifically, each company was asked to name somebody with an informed view about how the system works (e.g. the person who made the LEV specification, or knew its specification perhaps for maintenance purposes etc.). They were management or safety focused but not task focused i.e. not usually required to use the LEV.

• Employees (‘Users’) – were defined as individuals who made day-to-day use of the LEV equipment, and were task focused.

In addition, three differing types of LEV system were sought within the sample that covered fixed, movable and mobile LEV and consisted of enclosing, receiving and capturing hoods. The sample was not designed to gather data on all types of industry that use LEV equipment, but a good spread of industry types was attempted within the confines of the project.

The target sample aimed to include 10 small (<50), 5 medium (50 – 250) and 5 large (>250) businesses within the geographical areas of Cheshire, Derbyshire, Greater Manchester, Nottinghamshire, Staffordshire and South Yorkshire.

HSL generated the initial list of potential businesses using the HSE MINT database (containing business name, type, size and contact details) in conjunction with Standard Industrial Classification (SIC) codes (Appendix 1) within the manufacturing sector. A specialist recruitment company was then enlisted to recruit the participants for the study, using their own database, based on the SIC codes, because it was found that the MINT database was missing vital data relating to the businesses.

HSL provided the recruitment company with a recruitment letter (Appendix 2) and a screening questionnaire (Appendix 3), for use when contacting the businesses directly by telephone. Once businesses were recruited the HSL researcher then contacted the relevant HSE inspectors to check that there were no outstanding enforcement issues that would prevent participation in the study.

Whilst the final sample size fell short of the intended sample by one participant, the costs outweighed the benefits in pursuing the final participant.

The sample was purposive, which means that the sample was selected on the basis of the aims and objectives of the research, and in line with the qualitative approach. So although the findings cannot be generalised to the industry at large, the findings will be indicative of practices in the manufacturing sector, within the study's geographical area and to those manufacturers carrying out the processes covered within the sample.

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2.2

A consent form (Appendix 4) was given to the participants to sign and covered data protection, anonymity and right to withdraw. These ethical considerations are in line with the British Psychological Society’s (BPS) ethical guidelines. Finally, as a thank you for participating in the research each employer was given a free copy of the HSE book HSG 258 ‘Controlling airborne contaminants at work’, A guide to Local Exhaust Ventilation (LEV). In addition, employers and employees were also given the choice of either receiving a high street voucher or a donation on their behalf to the British Lung Foundation (BLF).

DATA COLLECTION TOOLS

A set of 2D line drawings was developed for use in conjunction with a semi-structured interview schedule. The 2D line drawings served to illustrate participants’ perceptions in relation to LEV hood positioning, contaminant behaviour and the capture zone (area of suction around the hood). The questionnaires aimed to provide discourse in order to map the use and effectiveness of LEV.

Tool 1

The first tool consisted of seven two-dimensional (2D) line drawings for the participants to use (Appendix 5) in relation to the following situations:

Decanting powder Vat/Barrel Large disc cutter

MIG welding Small disc cutter/grinder Soldering

Template (generic)

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The template 2D line drawing was produced so that it could be adapted if none of the operator tasks in the other line drawings related to the participant.

A secondary element, to be used in conjunction with the 2D line drawings, were cut-outs of two types of LEV (capturing and receiving hood), one large and one small of each type (Appendix 6). Participants were asked to place one of the LEV cut-outs on to the 2D line drawing for the positioning task. The line drawings and the LEV cut-outs pictures were designed roughly to scale and the task and the hood combination was chosen on the advice of HSE/HSL LEV experts. In addition, a video (sourced and produced by HSL) and script were produced to be used with the line drawings (Appendix 7) to help the participants familiarise themselves with the task.

Tool 2

The second tool consisted of two semi-structured question sets, one specific to employers and one specific to employees (Appendix 8 & 9). The difference between them was that the employee questionnaire had some questions on use and maintenance responsibility, and the employer questionnaire had a question relating to reasons for using LEV and a question relating to advice and/or experience of dealing with suppliers, designers and installers.

The aim of this tool was to gather a range of demographic data, use and effectiveness data and tool feedback data. The demographic questions related to job, role, responsibilities and experience, LEV make/model and use, safety precautions, maintenance, explanation for using LEV, experience of suppliers, designers and installers, safety precautions, training and the principles of LEV operation.

The main body of the questionnaire focused on effectiveness and use of LEV and included questions on positioning, capture zone and contaminant behaviour. There were also some questions relating to the effectiveness of LEV. For instance, what would make the LEV more or less effective and the advantages and disadvantages of LEV. Finally, there were some questions on LEV performance and a question on what they thought worked in a similar way to LEV.

The final part of the questionnaire aimed to obtain feedback on the question set and the 2D line drawings.

2.3 PROCEDURE AND TOOLS TEST

The questionnaires and 2D line drawings were trialled in workshops at HSL in order to test their usefulness, to highlight any improvements and to test the time it would take to conduct the interviews.

2.4 DATA COLLECTION

Once participants were identified a HSL researcher visited each business to conduct face-to-face interviews. The interviews started with general introductions, explanation of ethics, why the research was being conducted as well as outlining the procedure.

The interview was initiated using the appropriate questionnaire beginning with questions to gain background information on the business, individual, LEV type/use etc. before exploring perceptions of effectiveness and use. The 2D line drawings and cut-out LEVs were introduced when the questions relating to positioning, contaminant behaviour and the capture zone were being asked. At these points the participants were asked to select the most relevant line drawing (but adapted the template if no appropriate line drawing was relevant) and to select one of the

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four cut-out LEVs. Participants were then shown a short video clip that related to the 2D line drawing and the researcher read the corresponding passage from the video script, which explained the task, tool used and the type of contaminant being produced.

In the first task, ‘pin on the LEV’, participants were asked to place the relevant LEV cut-out onto the 2D line drawing where they thought it should be best positioned in relation to the task. The researcher then drew around the cut-out LEV and marked it (1). Participants were then asked further questions relating to positioning and re-positioning from the questionnaire.

In the second task, ‘contaminant behaviour’, the participants were asked to draw how the contaminant behaved using pen or pencil from the task/source of contaminant towards the LEV hood and the researcher then marked it (2). The participants were then asked questions relating to contaminant.

In the final task, ‘capture zone’, participants were asked to draw their interpretation of what a capture zone should look like, again relating it to the actual LEV and the situation in the 2D line drawing. The participants then drew in pen or pencil the shape of the capture zone and the researcher marked it (3). The participants were then asked specific questions relating to the capture zone.

After the three tasks were completed, participants were then asked questions exploring effectiveness and use of LEV that also included some questions on performance and what LEV was similar to. Finally, the questionnaire finished with some round up questions relating to the research tools employed. The researcher took written notes and also recorded participants’ verbal responses on a digital dictaphone. On completion of the interview, the participants were debriefed and thanked for their time.

2.5 DATA ANALYSIS

There were two distinct elements to the analysis; the qualitative analysis of the participant responses and an LEV expert analysis of participants’ 2D line drawings.

2.5.1 Qualitative analysis

Firstly, the researcher transcribed the data from all the interviews. The transcripts were then analysed based on the NATCEN (National Centre for Social Research) approach3 using MS Excel to create an analytical framework.

There were three stages to the qualitative analysis:

1) Data management: Identifying initial concepts/themes, tagging the data, sorting the data and summarising/synthesising the data.

2) Descriptive analysis: Identifying elements and dimensions and establishing typologies.

3) Explanatory analysis: detecting patterns of association, developing explanations and seeking wider applications.

At different stages of the analysis a HSL psychologist viewed a proportion of the data to check the reliability of the analysis. Inter-rater reliability assessment was carried out in order to achieve concurrence on the created categories and the major themes and sub themes. The level

3 For more information see NATCEN hyperlink in the references section 5

of agreement within this process was 95% and so some revision of the categories and a re-work of the major factors and themes was needed to make the analysis both reliable and valid.

2.5.2 LEV expert analysis of the 2D line drawings

A HSL LEV expert reviewed all the participants’ line drawings and scored them out of a possible 10 on three counts: positioning, contaminant behaviour and the capture zone. Scores between 0-3 were classified as poor, 4-6 average and 7-10 good.

In addition, the expert also looked for various elements when scoring for positioning, contaminant behaviour and capture zone.

• For positioning, the expert judged it on being as close as possible to the source;

• For contaminant behaviour, they judged it on being dependent on the process e.g. a hot process, contaminant rising and expanding or an energetic process e.g. directional and expanding (but not rising);

• For capture zone they judged it on the shape and size.

For each case (participant) the HSL LEV expert also added some additional comments relating to the 2D line drawings followed by a brief overview of the results. Some collaboration was required between the researcher and the LEV expert in order to reach a consensus on the interpretation of the 2D line drawings, the scoring and the additional comments. Finally, the LEV expert also had access to the qualitative results relating to positioning, capture zone and contaminant behaviour to help in interpreting the 2D line drawings.

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3 FINDINGS

3.1 SUMMARY DEMOGRAPHIC INFORMATION

The following section describes demographic data relating to the companies that were visited by the researcher.

3.1.1 Final sample overview

In total, 21 businesses were recruited for the sample which consisted of 8 small, 8 medium and 5 large businesses. Within the sample there were 20 employers and 39 employees totalling 59 participants (or cases).

3.1.2 Business type

All of the businesses that were recruited came from the manufacturing sector. The range of manufacturing consisted of chemicals, chemical products and man made fibres, rubber and plastic products, other non-metallic mineral products, basic metals and fabricated metal products, machinery and equipment, electrical and optical equipment and transport equipment.

3.1.3 Process

Most of the processes employed within the sample consisted of welding, grinding and cutting of metal and plastics, paint spraying, chemical mixing, electroplating, weighing and soldering. In addition, there was a blend of hot, cold and energetic processes.

3.2 QUALITATIVE ANALYSIS

The results of the qualitative analysis are presented as an illustration in Figure 1, which depicts the main factors and themes identified. This is then followed by a description of the factors, themes and sub-themes that were identified for both employers and employees. Within the text, misperceptions and overconfidence in LEV were highlighted within the context of use and effectiveness that the factors span. Finally, there were also some key quotes that have been inserted at the end of each factor, for both employers and employees, in order to highlight the main misperceptions, overconfidence and other pertinent issues relating to LEV use and effectiveness.

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ACCESS TO THE JOB

CONTAMINANT CHARACTERISTICS

ANALOGY

LEV SYSTEM DESCRIPTION

PROXIMITY CAPTURE ZONE EFFECTIVENESS

COMPONENTS LINE OF SIGHT CONTAMINANT CHARACTERISTICS

PROCESS CAPTURE ZONE SHAPE & SIZE

POSITIONING

EFFECTIVENESS AND USE OF LEV

INTERPRETATION OF THE CAPTURE

ZONE

NO TRAINING

DEGREES OF TRAINING

CONTROLS

BENEFITS OF LEV

DRAWBACKS OF LEV LEARNING & ADVICE FROM OTHERS

FORMAL TRAINING USER SAFETY

FACTORS OF EFFECTIVENESS

ATTITUDES TOWARDS LEV

PROTECTS BREATHING ZONE

CLEAN/SAFE ENVIRONMENT

POOR OPERATOR BEHAVIOUR

MAINTENANCE & SERVICING

IMPRACTICAL

LEV POWER/SUCTION

USE

Figure 1 Employer and employee factors of effectiveness and use of LEV

PPE/RPE REMOVES NEED FOR PPE

NO CONTROLS OR PPE COST

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3.2.1 Employer and employee factors, themes and sub-themes

Firstly, some definitions are required. The factors are the main topic areas that were identified, the themes are the elements within the topic areas and the sub-themes are constituent parts of the elements.

Employer responses will be presented first followed by employee responses. Within each group, under each factor, the main themes will be presented along with sub-themes or other statements and will include any misperceptions and overconfidence as well as key quotes. Themes will be presented in bold, misperceptions and overconfidence underlined and quotes in italics.

3.2.1.1 Controls (or safety measures)

Employers and employees were asked about what safety precautions they used when using LEV and the main themes that emerged were, ‘use of ‘PPE/RPE’ and ‘no controls or PPE’.

Employers: Typically employers stated that personal protective equipment (PPE) and respiratory protective equipment (RPE) was not used (no controls or PPE) when using LEV. However, other employers stated that PPE/RPE was used. Other statements included LEV being primary a control in itself, testing and inspection being important, assessing and eliminating risk and using contaminant suppressants as controls.

Employees: As with employers, employees in general stated that no controls or PPE was used, but others used PPE/RPE. Those who did not use any controls or PPE though stated that it was either optional or not a requirement. Other statements mentioned having shields next to the LEV to act as a control.

3.2.1.2 Degrees of training and sources of advice

Employers and employees were asked about the level of training they had on LEV and the main themes that emerged were ‘no training’, ‘formal training’ and ‘advice from others’.

Employers: Typically employers had no training or had received some formal training that consisted of either a NEBOSH diploma, a generic Health and Safety course or some form of basic training. In terms of advice from others, employers gained this from manufacturers, suppliers, installers, contractors, insurance inspectors or HSE.

"I think it was HSE, he had a mini LEV, I remember it vividly, he was showing us the effects of capture, just moving the hood away (proximity), remarkable...a good day all round, so you may constitute that as gaining knowledge" (15A)

"We would rely on the specialists" (18C)

Employees: Like employers, employees in general had no training on how to use LEV, whereas other employees had attended some formal training such as a welding course, generic Health and Safety course or some basic training. Other statements referred to relying on observation and experience and that LEV operation was simple or common sense. Other employees had read HSE guidance and others stated a need for training on other aspects of the LEV system. In terms of advice from others, employees either received it from employers, peers or installers.

"Basically if a new vacuum cleaner comes in, It’s just a case of here you go lads, here it is and how you use it" (5B)

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"As a welding engineer I should know more about the physics of it" (11B)

3.2.1.3 LEV system description

Employers and employees were asked how LEV worked in principle, what the LEV system comprised of and what they thought LEV was similar to. The main themes that emerged were ‘process’, ‘components’ and ‘analogies’.

Employers: In terms of the description of the LEV system employers typically described the process of how LEV worked in that LEV removed or extracted harmful contaminant (protecting the operators breathing zone) and that it was vented or extracted outside to atmosphere or recycled. Employers also knew about the components of LEV such as filters, fans, pipes (or hoses and ducting) and motors. Other statements mentioned the action of the fan in relation to airflow and of negative pressure. In terms of analogies employers stated that LEV was similar to a vacuum cleaner, chimney and natural ventilation (open doors and windows).

Other statements of similarity included fans, venturi, blowers, air conditioning systems, leaf blowers, cooker hoods and air movers.

"It's like a Hoover, a vacuum that sucks contaminants out from the air…catches it in a filter” (4A)

Employees: As for employers, employees in general described the process of how LEV worked in that the LEV extracted harmful contaminant (protecting the operator’s breathing zone) and that the contaminant was vented outside to atmosphere or recycled. Other statements referred to suppressants, that the LEV collects contaminant, protects the environment, that water and coolant is recycled and that LEV makes contaminant safe. Employees also considered the components of LEV such as filters, pipes (tubes, ducting), fans and other individual statements referred to other components such as the LEV being a system, worked by suction, had a motor, pump, alarm indicators and an on/off switch. In terms of analogies, employees typically thought that LEV was similar to vacuum cleaners and cooker hoods.

Other statements of similarity included extractors e.g. bathroom, chimneys e.g. flue, air or steel pumps, car exhausts, airlines, plasmas, tornados, venturis and an NVC unit (air conditioning unit on a tank).

"Well basically all I know is that it sucks away the actual fumes/dust…whatever it is" (4B)

3.2.1.4 Positioning (including re-positioning)

Employers and employees were asked about what sorts of things they considered when positioning and re-positioning LEV and the main themes that emerged were ‘protecting the breathing zone’, ‘having a good line of sight’, ‘proximity’, ‘having access to the task’ and ‘contaminant characteristics’.

Employers: In relation to positioning employers typically thought that protecting the breathing zone and having a good line of sight was important. In addition, they considered proximity of the LEV in terms of positioning the LEV hood as close to the task/job as possible, but not too close to affect the gas shield, and having the LEV hood correctly positioned at the right distance. Having access to the task so as to not obstruct the operator was considered as was contaminant characteristics such as contaminant properties in terms of amount, speed, weight, energy and size. Contaminant behaviour was also highlighted, especially that hot contaminant is likely to rise and that draughts have an influence on the behaviour of the contaminant. Other employers also stated that positioning was dependent on the task, material, contaminant, the

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LEV location, work piece, tool speed/positioning and the actual power and flow rate of the LEV. In addition, employers thought that capturing the majority of the contaminant determined adequate LEV positioning.

Other statements that were mentioned included positioning the airflow to allow for air to be replaced from what the LEV was removing and to position the LEV in order to avoid hazards like slips, trips, kinked hoses and fire risks. Finally, others stated that the capture zone of the LEV needed to be considered, that positioning was simple or common sense or conversely positioning was difficult to judge, the operator moving position and that total enclosure of the LEV was the best solution.

"Near the task in hand, its where it needs to be to get the vapour to go down the tubes…it does not want to linger too much within the atmosphere before it gets to the persons head area" (2A)

"You don’t want to be positioning so it obstructs the view of the operator" (7A)

Employees: For this group employees in general stated that having a good line of sight to the task was important when positioning LEV. In terms of proximity, like employers they considered that the LEV should be positioned as close to the task as possible, but not too close to affect the task e.g. affecting the gas shield or to damage the hood. Others stated that the LEV hood should be positioned over the top/above or angled to the side in relation to the task and the contaminant. Like employers, employees also stated that the LEV hood should be correctly positioned, but that this was a fine line/balancing act to achieve. Consistent with employers, employees also mentioned that optimum positioning is when the majority of the contaminant is being extracted and that positioning should be done to protect the breathing zone. Other employees also saw that positioning was dependent on the power of the LEV, the type of material being worked on, the location, the job, the operator moving position, changes in tool angle and contaminant amount and type. Contaminant characteristics such as contaminant behaviour also mirrored employers as employees stated that positioning judgement includes anticipating the contaminant, that hot contaminant rises which can be influenced by draughts. Having access to the job was also important, but other employees also talked about positioning judgement being gained from experience, but also highlighted poor operator/user positioning and behaviour.

Other statements related to contaminant properties (especially its weight), when the LEV was not in use or when changing the material or work piece. Suggested solutions to positioning included using more than one LEV or conducting a quick test. Barriers to positioning included having to move the LEV when welding which impacted on the weld itself and the issue of having to wear PPE as a requirement.

"You can’t see what you are doing if it’s in your line of sight, you have to angle it a bit to one side" (2B)

“It can get in the way of what you are doing, so sometimes you have to move it out of the way"(2C)

3.2.1.5 Interpretation of the capture zone

Employers and employees were asked about what influenced their interpretation of the capture zone, what it looked like, how they experienced it and how contaminants interacted with it. The main themes that emerged included ‘capture zone shape and size’, ‘contaminant characteristics’ and ‘capture zone effectiveness’.

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Employers: In terms of the capture zone shape and size employers typically stated that it was stronger in the centre and weaker at the sides, follows the 45 degree angles of the hood to the workbench or follows the 45 degree angles of the capture hood and eventually tapers in. Employers also thought that the capture zone was based on the size and shape of the hood, had a wide range of capture, recaptured contaminant once it had risen past the hood and was not based on the hood diameter. Generally employers thought that it was either arc or column shaped or a blend of the two.

However, employers sporadically had correct perceptions and confidence in the LEV. They thought that the capture zone shape and size was determined by the flow rate of the LEV, rejected the assumption that the capture zone followed the line of the hood, that the capture zone was based on the hood diameter, and that recapture of contaminant was unlikely. They rejected the assumption that it was based on the hood shape and that the capture zone pulled air from all directions around the hood and that vortices occurred at the sides of the hood. In addition, these employers thought that the capture zone was either elliptical or spherical.

In relation to capture zone effectiveness employers typically stated that incorrect positioning, blockages and draughts affected the LEV capability. Other statements included movable LEV, age and deterioration of the LEV, vortices, contaminant type, flow rate and LEV not being able to capture all contaminant made LEV less effective. In contrast, other employers thought that matching the LEV to the task made it more effective and that LEV was generally effective. Other statements included LEV being effective within the hood diameter range, fixed LEV being 100% effective, that contaminant type determined LEV effectiveness and that LEV effectiveness or capability could be ascertained by tests and indicators and that demonstrations or training would also help in determining it.

In terms of contaminant characteristics employers typically stated that hot contaminant rises and expands, that it is recaptured, but that it also escaped. Other statements included the contaminant swirling, predictable as well as unpredictable, being dense then becoming diffuse, more contaminant at source and the contaminant being narrow or being pulled in a line towards the LEV. Finally, the properties of contaminant were considered such as density, size, speed, gravity and its visibility.

"Hopefully sucks it back in again…drags it back up again” (1A)

"Although it will capture it where the fan fans out it won’t be as strong as in the centre of the hose…I probably know this from experience...you can just imagine the air going down the hose" (6A)

"The LEV is there to do a job because obviously the LEV has to capture it all" (6A)

"From when I have seen it, the closer you get to it, it forms a blob like that and you can see it being pulled away, just pulled in a train away from where its being generated" (9A)

“I do think its misleading to a certain extent because people may think it comes down direct, it loses it at the edges…they may see it as being a replica of a light (1950’s light) light will come down only because we don’t see it doing that because of the speed of light” (20C)

Employees: In terms of the capture hood shape and size employees generally stated that it was stronger in the centre but weaker at the sides, followed the angle of the capture hood down to the workbench or tapering in slightly the further away from the hood face, recaptured contaminant that had risen past the sides of the hood, influenced by the shape and size of the hood and that the capture zone had a large range. Typically employers thought that it was shaped like a triangle, cone or conical, arc, column (oblong) or semi-circular.

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In relation to capture zone effectiveness employees on average stated that the LEV would have less capability if it was positioned too far away, was a large LEV system, dependent on the age and condition of the LEV or if they were mobile hoods. Other statements included things like the LEV not being 100% effective and the capture zone not being very large. In contrast, other employees thought that more suction or power, close positioning and good operator positioning as well as working in a draught free environment would make LEV more effective. Other statements relating to effectiveness included things such as the design of the LEV, the range of the LEV being 1-2ft, being 100% effective and the capture zone being based on the hood shape.

In terms of contaminant characteristics employees typically stated that it tended to get dragged, that it swirls, that hot contaminant rises and expands, recaptures, escapes and is predictable and unpredictable. Other statements included the contaminant being taken for granted, multi-directional and that contaminant behaviour is observed and based on experience as well as the contaminant shape being shaped either like a pyramid or bell. In terms of contaminant properties employees tended to talk about its weight, size, gravity, speed and whether it was visible or invisible. However, other statements included the contaminant being drawn into the LEV in a straight line and that certain tools accelerate contaminant.

"With it being a hood the main extraction will come from that line itself...where the bottom of the hood expands but it will be stronger in the middle" (8B)

"Others are fooled by the hood shape...with obviously not being shown how to use it....I don't think they work in a big arc, they are not powerful enough to do that" (16B)

"It’s just the perspective that I have got is that because it’s a smaller hood it wont extract as much as a normal hood, more scope, more capture...probably as still as wide...it does follow the line of the hood as I understand it" (16C)

"I think it will come out level with the shape of the hood so if your hood like has an angle on it, it will come out but the further it goes it's going to reduce and come in” (19C)

"We need to learn all this sort of thing what you are asking" (20B)

3.2.1.6 Attitudes towards LEV

Employers and employees were asked about the advantages and disadvantages of LEV and the main themes that emerged as benefits included ‘protecting the user/operator’, ‘a clean and safe working environment’ and ‘reducing the need for PPE’ and for drawbacks, ‘cost’, ‘poor operator behaviour’ and ‘LEV being impractical’.

Employers: In relation to the benefits of LEV employers typically stated that LEV helped protect the operator and other employees, helped to maintain a clean and safe working environment and removed the need for PPE. Other statements included the LEV being an engineering solution, removing the threat of litigation, removing operator judgment (on certain types of LEV), kept sickness absence down, helped to maintain a constant productivity, gave piece of mind and helped staff morale. In relation to the drawbacks of LEV in general employers stated that cost, poor operator behaviour/use and a poor appreciation of risk awareness. Other statements included the issue of getting access to the task, LEV being noisy and time consuming to start up, breakdowns, LEV causing a whole new set of issues, that the hood shape was misleading and that re-positioning judgment was problematic.

"There is a perception of no risk here" (9A)

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"Better working environment and you’re not contaminating anyone's lungs or anything like that" (12C)

Employees: In relation to the benefits of LEV employees generally stated that LEV helped to protect the operator and employee and helped to maintain clean and safe working environment. Other statements included the LEV being practical, that fixed LEV was preferable and that LEV was effective if maintained. In relation to the drawbacks of LEV operators stated that LEV was impractical to use on some jobs, that LEV had no disadvantages, was noisy, caused an obstruction and was difficult to use when working in confined spaces. Other statements included the LEV involved constant repositioning, positioning judgement, having to use PPE, breakdowns, dropping arms on capture hoods, removing the gas shield when welding, that some LEV was uncomfortable to use and that LEV caused additional hazards.

"It takes the mist out of the air... it keeps it off our chest" (3B)

"They are all effective because they would not be made, or put there, they just need to be maintained" (12A)

3.2.1.7 Factors of effectiveness

Employers and employees were asked about what could make LEV more or less effective as well as their opinion of general effectiveness. The main themes that emerged were ‘maintenance and servicing’, ‘LEV power’ and ‘use’.

Employers: In relation to what would make LEV more effective employers typically stated that increased LEV power, correct positioning/use, regular maintenance and servicing and matching the LEV to the task would help. Other statements included changing the size of the physical characteristics of the LEV e.g. shorter hose, larger fan, motor or hood. In addition, better operator information e.g. training and education, LEV being partially enclosed, having good suppliers and installers and visual indicators on the LEV would help make LEV more effective. In contrast employers typically stated that malfunction or damage to parts of the LEV, blockages, incorrect use and poor maintenance and checks would make LEV less effective. Other statements included poor airflow/flow rate, the LEV not being switched on, positioned too far away, poor design, the actual contaminant type, contaminant build up and open ducts on other LEVs within the system that would make LEV less effective. In term of general effectiveness employers thought that LEV was not 100% effective, that poor installation was an issue and that mobile LEV was poor. In contrast, other employers thought that LEV eliminated the risk, was 100% effective, matching the LEV to the task was critical and good maintenance made LEV more effective.

"…I guess a step back from that importantly is to specify it correctly in the beginning, selecting a reputable supplier to work with, somebody who is a proper LEV company not just a general fabricating company" (15A)

"If you get the right spec for the right job, if you give all your information on what you are actually doing and what you want it to do then you will get the right extractor providing you. what you are doing, what steels you are using…as much as you can...getting the best one for the right job" (17A)

Employees: In relation to what would make LEV more effective employees in general stated that it depended on the LEV power, the task, and contaminant type (including properties). Generally though more LEV power, bigger or different shaped hoods, correct positioning and use, cleaning and regularly changed filters (maintenance and servicing) and the LEV being matched to the task would make LEV more effective. Other statements included total enclosures

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3.3

being the best solution, a well maintained LEV, better location and workspace for LEV, having flexible hoses and grills fitted to the inside of the hood and operator knowledge would increase effectiveness of LEV. In contrast, employees typically stated that blockages (filters and ducts), incorrect use and positioning, poor maintenance and servicing and impractical use of LEV made them less effective. Other statements included the LEV causing barriers to using it properly, less LEV power, smaller or incorrect LEV, motor and tubing, nothing making LEV ineffective, draughts, incorrect measurements of airflow/flow rate, faulty parts, age and condition of the LEV, using a bigger LEV for the work, positioning too close causing damage, poor matching of LEV to task and poor operator judgment would make LEV less effective. In terms of general effectiveness employees thought that LEV was very effective and that capture hoods, fixed rim-lip extraction and push and pull systems were good and that LEV had a good range of capture. In contrast other employees thought that LEV was not 100% effective and that mobile and receiving hoods were poor and that poor maintenance made LEV less effective.

"The extraction in our bays are very strong, if you are too close it will pull you to it...stick to it, it’s quite strong...I have been too close sometimes and it pulls your head or mask and I pulled myself off it (10B)

"If you had a different hood instead of just being a round one, a longer narrower one…a different shape of hood" (19B)

EXPERT RATING OF 2D LINE DRAWINGS

A HSL LEV expert rated all the participants’ responses on the 2D line drawings on a scale of 0-10 on three elements: positioning; capture zone; and contaminant behaviour. Scores between 0-3 we classified as poor, 4-6 average and 7-10 good. In addition, the expert also highlighted any misperceptions within these three elements. Table 1 summarises employers’ and employees’ scores on positioning, capture zone and contaminant behaviour as well as stating combined scores.

Table 1 LEV Expert rating of participant’s 2D line drawings

Positioning Capture Zone

Contaminant behaviour

Employers 8.5 (8.8)* 4.2 6.9 Employees 7.2 (7.3)* 4.4 6.0 Overall 7.9 (8.1)* 4.3 6.5

* Within the positioning task, some of the participants drew two hoods which were given two scores by the LEV expert and therefore the scores in brackets reflect this. The other scores are for one hood only.

Employers’ scores were the best on positioning (8.5) followed by contaminant behaviour (6.9) whilst the worst score was for the capture zone (4.2).

Similarly, employees’ scores were the best for positioning (7.2) followed by contaminant behaviour (6.0) and the worst score was the capture zone (4.4).

3.3.1 Summary of employer misperceptions

There were several misperceptions relating to the capture zone drawn by some employers such as it being too large, the wrong shape, following the line angle of the hood (capture hood) and

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being cone shaped. However, some employers had a correct perception of the capture zone being spherical.

Graphical example of a misperception and overconfidence of the capture zone:

In this 2D line drawing (by participant 9A) position 1 was given a score of 10/10, position 2 was given a score of 6/10 but the capture zone was given a score of 6/10 because the participant drew an imaginary line extending from the hood which is not correct, although the distance of capture is correct.

3.3.2 Summary of employee misperceptions

There were also several misperceptions relating to the capture zone drawn by some employees such as it followed the line/angle of the hood, was too large, the wrong shape, cone shaped or an angled cone, column shaped or a narrow column.

Graphical example of a misperception and overconfidence of the capture zone:

In this 2D line drawing (by participant 10B) position 1 was given a score of 10/10, position 2 was given a score of 5/10 but the capture zone was given a score of 4/10 because the participant

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drew an imaginary line extending from the hood extending towards the workbench which is not correct in shape nor distance.

Other graphical representations of employers and employees positioning, contaminant behaviour and capture zone are included in Appendix 10.

The HSL LEV expert also stated that most of the diagrams drawn of the capture zone on the 2D line drawings were incorrect.

“Many of the drawings show a fan shaped capture zone…this is incorrect, however, if positioned above a hot rising plume the capture zone would be an odd shape and would be elongated” (LEV Expert).

3.4 SUMMARY OF KEY FINDINGS

Table 2 summarises both employers and employees results within the seven factors identified from the qualitative analysis. The table provides a direct comparison between employers and employees, and it also highlights the themes and sub themes within each of the seven factors. This summary should be viewed in conjunction with the rich, contextual, and detailed qualitative data provided in the Main Findings (Section 3). Note: misperceptions and overconfidence are highlighted within the table in bold.

Table 2 Summary of key findings from the semi-structured interviews: Employers & Employees

Employers Employees ‘Controls’ (Section 3.2.1.1)

Theme Sub-theme Theme Sub-theme PPE/RPE used N/A PPE/RPE used N/A No controls/RPE N/A No controls/RPE N/A

‘Degrees of training and sources of advice’ (Section 3.2.1.2) Theme Sub-theme Theme Sub-theme No training No training >Simple/common sense

>Observation and experience Formal training >NEBOSH course

>H&S course >Basic training

Formal training >Welding course >H&S course >Basic training

Advice from others >Manufacturers >Contractors >Installers >Insurance inspectors >HSE

Advice from others

>Employers >Peers >Installers

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‘LEV system description’ (Section 3.2.1.3)

Employers Employees Theme Sub-theme Theme Sub-theme Process >Extracts harmful contaminant from

the air and vents or recycles >Protects the operators breathing zone

Process >Extracts harmful contaminant from the air and vents or recycles. >Protects the operators breathing zone

Components >Filters >Fans >Pipes >Motors

Components >Filters >Pipes >Fans

Analogies >Vacuum cleaner >Chimney >Natural ventilation

Analogies >Vacuum cleaner >Cooker hood

‘Positioning’ (Section 3.2.1.4) Theme Sub-theme Theme Sub-theme Protect the breathing zone

Protect the breathing zone

Having a good line of sight

Having a good line of sight

Proximity >Close as possible >Not too close to affect gas shield

Proximity >Close as possible >Not too close to affect gas shield

Having access to the task

Having access to the task

Contaminant characteristics

>Contaminant properties >Contaminant behaviour


>Contaminant behaviour

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‘Interpretation of the capture zone’ (Section 3.2.1.5)

Employers Employees Theme Sub-theme Theme Sub-theme Capture zone shape and size

>Stronger in centre weaker at sides >Follows 45 degree angle/line of hood >Based on shape size of hood >Wide range of capture >Recaptures contaminant >Not based on hood diameter >Arc or column shaped

Capture zone shape and size

>Stronger in centre weaker at sides >Follows 45 degree angle/line of hood >Recaptures >Influenced by shape & size of hood >Wide range of capture >Triangle, cone, arc, column shaped


>Hot contaminant rises >Expands >Recaptured >Escapes


>Contaminant dragged >Swirls >Hot contaminant rises >Expands >Recaptures >Escapes >Predictable/unpredictable

Capture zone effectiveness

>Incorrect positioning >Blockages >Draughts

Capture zone effectiveness

>Less effective if positioned further away >Better if a larger system >Depends on the age/condition of the LEV

‘Attitudes towards LEV’ (Section 3.2.1.6) Theme Sub-theme Theme Sub-theme Benefits >Protects the user/operator

>Clean safe working environment >Removes the need for PPE

Benefits >Protects the user/operator >Clean and safe working environment

Drawbacks >Cost >Poor operator >Behaviour/use

Drawbacks >Impractical

‘Factors of effectiveness’ (Section 3.2.1.7) Theme Sub-theme Theme Sub-theme More effective >LEV power

>Correct positioning/use >Servicing & maintenance

More effective >LEV power >Correct positioning and use >Servicing and maintenance

Less effective >Incorrect use >Poor servicing and maintenance

Less effective >Incorrect use and positioning >Poor servicing and maintenance >Impractical use >Less LEV power

The results from both employers and employees were similar across most of the factors with minimal divergence of themes and sub themes. Most of the factors showed that both groups had a good appreciation of the issues relating to LEV use. However, both groups provided similar responses in relation to misperceptions and overconfidence that are clustered within the factor ‘interpretation of the capture zone’ and to a lesser degree within the factor ‘positioning’.

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Table 3 summarises the LEV expert’s analysis of the 2D line drawings, and again compares the results from employers and employees. The table is split into two parts; the first part relates to scores out of a possible 10 for participants sketches on positioning, capture zone and contaminant behaviour (A). The second part relates to misperceptions and overconfidence identified by the HSL LEV expert, when analysing the drawings (B). Note: misperceptions and overconfidence are highlighted within the table in bold.

Table 3 Summary of key findings from the 2D line drawings:– Employers & Employees

Employers Employees

2D line drawings (A) (Section 3.3)

Element Score (0-10) Element Score (0-10)

Positioning 8.5 Positioning 7.2

Capture Zone 4.2 Capture Zone 4.4

Contaminant behaviour

6.9 Contaminant behaviour

6.0

2D line drawings (B) (Section 3.3)

Too large

Wrong shape

Following line/angle of the hood

Cone shaped

Followed line/angle of the hood

Too large

Wrong shape

Cone or column shaped

The key results show that the capture zone is the least well understood within part A of the table for both employers and employees. In addition, in part B of the table there is also similar results between the two groups in terms of the main misperceptions and overconfidence in relation to the capture zone

Seen together, the qualitative analysis and the 2D line drawings both support the idea that there are misperceptions and overconfidence in LEV, but moreover that both types of analysis are congruent in that the capture zone is where the majority of the misperceptions and overconfidence occur and that most other aspects of LEV are well understood by both employers and employees in the sample.

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4 DISCUSSION

This study was undertaken because HSE had anecdotal evidence that both employers and employees had misperceptions and overconfidence in the effectiveness and use of LEV. The results of the study revealed that in general participants knew how to use LEV, but their knowledge of its effectiveness was mixed. Significantly there were many misperceptions and overconfidence regarding participants’ interpretation of the capture zone. In addition, employers’ and employees’ responses were very similar in most instances.

Findings from the qualitative analysis will be discussed first, followed by the results of the expert rating of the 2D line drawings, specifically in terms of misperceptions and overconfidence within the context of effectiveness and use.

Seven main factors emerged from the qualitative analysis. The first factor, ‘controls’ relates in part to the use of LEV. Use of PPE and RPE was mixed and of various types such as gloves, masks etc. Both employers’ and employees’ results were similar apart from employers who thought that LEV was the primary control, they stated the importance of testing and inspection, assessing and eliminating risk. In contrast, employees stated that no controls or PPE was needed because it was either optional or not a requirement.

The second factor, ‘degrees of training and sources of advice’ revealed that both employers and employees were similar in terms of their level of training. It was found that participants had very little or no training, or some formal training. Overall, the level of training on how to use LEV was non-existent or basic at most and only covered positioning and basic maintenance. In relation to advice, employers got their information from manufacturers, suppliers, installers, contractors etc. whereas employees relied on employers, peers, installers as well as observation and experience. The results suggest that generally the level of training was poor, only some of the basics of LEV use were known and that advice was being mostly sought from non-independent sources.

In the third factor, ‘LEV system description’, employers and employees generally understood how LEV worked (principle operation and components). Both groups knew that LEV protected the workers breathing zone, removed harmful contaminant from the air and vented it externally or recycled it. However, both groups also made incorrect comparisons about what worked in a similar way to LEV (e.g. like a vacuum cleaner, chimney, cooker hood or natural ventilation). Therefore, the results suggest both groups had a good understanding of how LEV worked in principle, but that their understanding of what equipment works in a similar way to LEV was misguided.

The fourth factor, ‘positioning’ also related to LEV use and again both employers and employees made similar judgements about positioning and re-positioning the hood. Both groups considered protecting the breathing zone of the operator, having a good line of sight, having access to the task, contaminant characteristics and proximity (i.e. being close but not too close). Although one misperception was that positioning the LEV too close would remove the gas shield. The results suggest that apart from the misperception in relation to the gas shield, both groups had a good understanding of the considerations when positioning LEV, but overall there were no clear differences in either groups’ responses.

The fifth factor, ‘interpretation of the capture zone’ revealed that both employers and employees had a cluster of misperceptions and overconfidence in relation to the capture zone. For example, both groups stated that the capture zone was stronger in the middle and weaker at the sides, followed the line/angle of the hood, had a wide range of capture, recaptured contaminant and

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was shaped like an arc, cone or column. However, some participants had correct perceptions i.e. knew not to be fooled by the hood shape or size, recaptured contaminant and was shaped like a sphere or ellipse, but these examples were rare. From the interviews with these specific participants it was found that they had a background mix of physics, chemistry and engineering or had read previous or current HSE LEV guidance.

The misperceptions and examples of overconfidence were widespread within this factor and suggests a lack of understanding of how the capture zone works. Perhaps this is to be expected if both groups have had limited training on LEV, which mainly focuses on positioning and maintenance. Furthermore, there is no surprise that both groups had these impressions of the capture zone if their primary guidance and advice came from manufacturers, suppliers and installers. The question is whether this information alone may be causing misperceptions and overconfidence in the capture zone. With a lack of information or incorrect information as to how a capture zone works it is plausible to think that employees (users) build a concept based on their available knowledge and experience. The problem for employees is that the capture zone is invisible, as are certain contaminants that behave in different ways. Both groups talked about contaminant characteristics and the results were similar in that they both talked about contaminant behaviour and contaminant properties. One misperception was that contaminant was recaptured, but this misperception was not held by all. However, the results did show that both groups had a good basic understanding of contaminant.

In relation to capture zone effectiveness, both groups’ responses were rather mixed. There were examples of misperceptions and overconfidence within this topic as some employees thought that the capture zone was based on the hood shape and some employers and employees thought that the capture zone was 100% effective. The results indicated that apart from some misperceptions and overconfidence, both groups knew what could make the capture zone more and less effective.

For the sixth factor, ‘attitudes towards LEV’, both employers and employees had similar responses to the advantages but both groups differed in relation to the disadvantages. The results suggested that both groups knew the benefits and drawbacks to using LEV. However, a possible overconfidence is the belief that LEV systems have no drawbacks. In addition, one interesting fact was that employers tended to blame the operator whereas the employee tended to blame the work for making LEV ineffective.

In the seventh and final factor, ‘factors of effectiveness’ both groups’ responses were similar in terms of what made LEV more or less effective i.e. LEV power, servicing and maintenance, and incorrect use. In addition, their results for general effectiveness were mirrored and both groups stated that mobile LEV was poor. The results suggest that although LEV effectiveness was mixed, there were some instances of misperceptions and overconfidence e.g. using a larger hood would make LEV more effective.

The second element of the analysis was the 2D line drawings that were analysed by the LEV expert. The quantitative scores revealed that both groups had greatest understanding of positioning (7.9), followed by contaminant behaviour (6.5), but there was a much poorer understanding of the capture zone (4.3). The LEV expert also found many misperceptions and overconfidence in the illustrations of capture zones, which supports the qualitative analysis. Participants in both groups drew large capture zones, drew a line mimicking the line/angle of the capture hood and drew cones/arcs and columns, when in fact the capture zone is more spherical and its size is based on the hood diameter. The results suggest that both groups had a large cluster of misperceptions and overconfidence in the capture zone. In addition, the results indicate that, although positioning is well understood, the capture zone and to a lesser degree the contaminant that interacts with it shows a gap in a critical aspect of LEV use.

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Overall, employers and employers knew some of the fundamentals of using LEV (i.e. safety measures, principle of operation, positioning, benefits and drawbacks). In addition, they had mixed views on the effectiveness of LEV in general. However, most of the misperceptions and overconfidence in the use and effectiveness, within both groups of participants, related to the capture zone, an essential pillar of LEV use. Therefore, this critical component needs to be communicated to both operators and employees. Essentially they need to know what the capture zone looks like and how it behaves. Finally, as contaminant (visible or invisible) is closely associated with the capture zone (invisible) it may also be worthwhile including some communication on how the contaminant interacts with the capture zone.

Further, there also appears to be a training need, because much of the information received by employers came from manufacturers, suppliers and installers rather than an independent source. For example, suppliers may inadvertently be exaggerating the range and power of the capture zone, which in turn is digested by employers and fed to employees (users). This could explain why these misperceptions and overconfidence are occurring but this is only speculative and not evidence based.

There is also an issue in relation to the installation of LEV: it must be installed properly, and employers need the right independent advice in order to know that the LEV system that they are purchasing will be matched to the task. Other topics that were highlighted within the research were poor operator behaviour and use, a perceived need by participants to get more training on LEV and the issue of poor installation and advice. Although this research focused on use and effectiveness of LEV in terms of misperceptions and overconfidence, it has also identified other factors that relate to the experience of using LEV.

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5 CONCLUSION

Overall, participants (employers and employees) knew most of the basic principles in order to use and operate LEV i.e. controls, process, components, positioning and the benefits and drawbacks to using LEV. In terms of effectiveness, participants’ responses were mixed in relation to capture zone effectiveness and LEV effectiveness in general. However, there were many instances of misperceptions and overconfidence in the interpretation of the capture zone identified in both the qualitative and 2D line drawings analysis.

Misperceptions and overconfidence clustered around the factor ‘interpretation of the capture zone’ more than any other factor, which indicates a critical gap in employers and employees knowledge of the use and effectiveness of the capture zone. Simply, knowing how the capture zone works and why it works is a fundamental pillar in understanding use and effectiveness of LEV.

The findings of this study provide evidence to support the anecdotal view that there are misperceptions and over confidence in the use of LEVs. The key results could be used by HSE as part of their wider communication strategy. In addition, misperceptions and overconfidence of LEV may be driven in part by manufacturers, suppliers and installers, employer and employee ignorance or lack of understanding of the capture zone. In order to address these common misperceptions and overconfidence it could be practical to target employers and employees specifically showing them how a capture zone works and how contaminants interact with it.

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6 REFERENCES

HSG258, (2008). Controlling airborne contaminants at work, A guide to Local Exhaust Ventilation (LEV) http://www.hse.gov.uk/pubns/books/hsg258.htm

Greaves, D and Holroyd, J., (2009). HSE Research Report, Perceptions of LEV: Scoping Study (RSU/09/17)

National Centre for Social Research (NATCEN) http://www.natcen.ac.uk/

National Statistics, UK SIC (2003), UK Standard Industrial Classification of Economic Activities http://www.statistics.gov.uk/methods_quality/sic/downloads/UK_SIC_Vol1(2003).pdf

The British Psychological Society (BPS), Code of Conduct and Ethical Guidelines (2006) http://www.bps.org.uk/the-society/code-of-conduct/

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7 APPENDICES

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APPENDIX 1: Standard Industrial Classification (SIC) codes

Manufacturing (D)

• Manufacture of wood and wood products (DD)

20.1, 20.10, 20.2, 20.20, 20.4, 20.40, 20.5, 20.51

• Manufacture of chemicals, chemical products and man made fibres (DG)

24.2, 24.20, 24.3, 24.30, 24.4, 24.41, 24.62, 24.7, 24.70

• Manufacture of rubber and plastic products (DH)

25.12, 25.13, 25.2, 25.23/1, 25.24

• Manufacture of other non-metallic mineral products (DI)

26.51, 26.52, 26.53, 26.6, 26.7, 26.70, 26.82/1, 28, 28.1, 28.11, 28.12, 28.2, 28.21, 28.22, 28.3, 28.30, 28.5, 28.51

• Manufacture of basic metals and fabricated metal products (DJ)

27.43, 27.5, 27.51, 27.52, 27.53, 27.54, 28.1, 28.11, 28.12, 28.2, 28.21, 28.22, 28.3, 28.30, 28.4, 28.40

• Manufacture of machinery and equipment not elsewhere classified (DK)

29.31, 29.41, 29.52/2, 29.6, 29.60, 29.71

• Manufacture of electrical and optical equipment (DL) (30/31)

Any of these with a mix of business size (30-33.50)

• Manufacture of Transport equipment (DM)

34.1, 34.10, 34.20/3, 35.1, 35.11, 35.3, 35.30, 35.42

• Manufacturing not elsewhere classified (DN)

36, 36.1, 36.11, 36.12, 36.21, 36.30, 37.1, 37.10, 37.2, 37.20

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APPENDIX 2: Recruitment Letter

Harpur Hill, Buxton Derbyshire, SK17 9JN Telephone: +44 (0)1298 218000 Facsimile: +44 (0)1298 218590

DD/MM/YYYY

Dear…

WHAT ITS ABOUT

The Health and Safety Laboratory (HSL) are conducting a study on behalf of the Health and Safety Executive (HSE) to gain some insight into employers and workers perceptions on how Local Exhaust Ventilation (LEV) works and how effective it is. This will help us to develop a communication strategy to improve the design, application and selection of LEV and moreover to keep people safe and healthy at work.

WHAT DO WE WANT

We need one employer (someone with good LEV system knowledge) and two employees (LEV users) to participate. The research involves us visiting your workplace and asking participants to:

• Look at some videos • Answer some questions • Complete a couple of paper based tasks

The research will take approximately 20 minutes per person and the data provided will remain anonymous so that the business or the individuals are not identified.

WHAT’S IN IT FOR YOU

As a thank you for participating in the research HSL will provide your company with £50 (a gift voucher or charitable donation of your choice) and a free paper copy of the new LEV guidance HSG258 “Controlling airborne contaminants” which includes a DVD. See http://www.hse.gov.uk/pubns/books/hsg258.htm. In addition, each participant will be provided with £10.

If you would like to participate, contact me either by phone or email.

Daniel Greaves

HSL Human Factors Researcher Human and Organisational Factors Team

Direct Tel: 01298 218419 Email: [email protected]

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APPENDIX 3: Screening questionnaire

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APPENDIX 4: Consent form

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APPENDIX 5: 2D LINE DRAWINGS

5.1 OPERATOR DECANTING POWDER FROM ONE CONTAINER TO ANOTHER

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5.2 OPERATOR NEXT TO A VAT/BARREL

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5.3 OPERATOR USING A LARGE DISC CUTTER

33

5.4 OPERATOR MIG WELDING

34

5.5 OPERATOR USING A SMALL DISC CUTTER/GRINDER

35

5.6 OPERATOR USING A SOLDERING IRON

36

5.7 TEMPLATE/GENERIC 2D LINE DRAWING

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APPENDIX 6

Small capturing hood (purex 30mm)

: CUT OUT LEV’S

Large capturing hood

Large Receiving hood 1

Small Receiving hood 2

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APPENDIX 7: SCRIPT FOR VIDEO SITUATIONS

a. Operator using a soldering iron with a small (capturing) hood

The LEV operator is soldering with so me solder fixing computer chips onto a circuit board, the process is em itting some hot fume.

b. Operator using a small disc cutter/grinder with a small (captur ing) hood

The LEV operator is using a small disc cutter/grinder to trim/polish som e metal and the process is emitting some metal dust/fume..

c. Operator decanting powder from one container to another with a large (capturing) hood

The LEV operator is moving some powder from one container to another, the process is emitting some fine dust.

d. Operator using a disc cutter with a large (capturing) hood

The LEV operator is using a disc cutter to cut through some stone, the process is emitting a lot of dust.

e. Operator MIG welding using a large (capturing/receiving) h ood

The LEV operator is welding some metal using a MIG gun and the process is emitting some hot fum e

f. Operator next to a hot process using a (receiving) hood

The LEV operator is monitoring a hot process which is emitting some hot fume/vapour?

39

APPENDIX 8: EMPLOYEE QUESTIONNAIRE

40

APPENDIX 9: EMPLOYER QUESTIONNAIRE

46

APPENDIX 10: GRAPHICAL REPRESENTATIONS OF EMPLOYERS AND EMPLOYEES POSITIONING, CONTAMINANT BEHAVIOUR AND CAPTURE ZONE

Employers

(5A) (9A) (8A)

(12C) (18C) (19A)

Employees

(10B) (11B) (12B)

51

(13A) (15C) (15B)

(18A) (20A) (20B)

52

Published by the Health and Safety Executive 02/11


Perception and understanding of how local exhaust ventilation (LEV) works and how effective it is: Phase 2 Background: Health and Safety Executive (HSE) inspectors had anecdotal evidence that employers and employees had misperceptions and overconfidence in LEV systems. Therefore, HSE commissioned the Health and Safety Laboratory (HSL) to gain insight into these users’ current understanding and perceptions relating to different types of LEV systems as well as compare and contrast the results of these two groups.

Methodology: A HSL researcher devised a bespoke methodology using a qualitative approach that consisted of semi-structured questionnaires, a series of 2D line drawings and cut-out LEV hood pictures. These were applied together in face-to-face interviews with a purposive sample of employers and employees from the manufacturing sector who owned/used LEV systems within the UK.

Results: Participants had an adequate understanding of the basic principles of LEV systems. However, many had limited training on LEV and most of their information came from manufacturers, suppliers and installers. There were many misperceptions and overconfidence in the use and effectiveness of LEV that were found specifically in relation to the capture zone (area of air suction around the hood).

Conclusion: Although employers and employees knew the basics of LEV use and operation there was a cluster of misperceptions and overconfidence in relation to the interpretation of the capture zone. Therefore, the results could be used by HSE as part of its wider communication strategy and in order to dispel misperceptions and overconfidence amongst employers and employees perhaps by showing them how a capture zone works and how contaminants interact with it.

This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the author alone and do not necessarily reflect HSE policy.

RR836

www.hse.gov.uk

perception and understanding of how local exhaust ventilation

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