P . S A I K U M A R

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M . P H A R M A C Y

P H A R M A C E U T I C A L C H E M I S T R Y

U N I V E R S I T Y C O L L E G E O F T E C H N O L O G Y

O S M A N I A U N I V E R S I T Y

LABORATORY DESIGN, SAFETY AND MANAGEMENT

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Designing laboratory – equipment

Heating devices

Ovens

Hot plates

Heating mantles

Oil, salt, or sand baths

Hot air baths and tube furnaces

Heat guns

Air conditioning systems

Types of air conditioning

Ventilation

Laboratory fume hoods

References

CONTENTS:

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The process of constructing a new laboratory revolves around four general

activities: planning, design, construction, and moving.

Specific activities vary within each phase of the process, and each stage.

Scope

The primary objective in laboratory design is to provide a safe environment

for laboratory personnel to conduct their work.

Therefore, all health and safety hazards must be identified and carefully

evaluated so that protective measures can be incorporated into the design.

Introduction

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The most common type of electrical equipment

Used to supply the heat needed to effect a reaction or separation.

The use of steam-heated devices rather than electrically heated devices is generally preferred whenever temperatures of 100 °C or less are required.

Because they don’t present shock or spark risks, they can be left unattended with assurance that their temperature will never exceed 100 °C.

General precautions:

Enclose the actual heating element in any heating device in a glass, ceramic, or insulated metal case to prevent laboratory personnel from accidentally touching the wire carrying the electric current. This construction minimizes the risk of electric shock.

Resistance devices used to heat oil baths should not contain bare wires.

If any heating device becomes so worn or damaged that its heating element is exposed, either discard the device or repair it before it is used again.

Be aware that dry and concentrated residues can ignite when overheated in stills, ovens, dryers, and other heating devices.

Heating Devices

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Electrically heated ovens to remove water or other solvents from

chemical samples and to dry laboratory glassware.

Never use laboratory ovens to prepare food for human consumption.

Purchase or construct laboratory ovens with their heating elements and their

temperature controls physically separated from their interior atmospheres.

Small household ovens and similar heating devices should not be used in

laboratories.

Vacuum drying ovens, discharge volatilized

substances inside the oven to form explosive

mixtures with the air.

This hazard can be reduced by connecting

the oven vent directly to an exhaust system.

Ovens

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Hot plates solutions are to be heated to 100 °C or higher and the

inherently safer steam baths cannot be used as the source of heat.

Use only hot plates that have completely enclosed heating elements in

laboratories.

Although almost all laboratory hot plates currently sold meet this criterion,

many older ones pose an electrical spark hazard arising from either the on/off

switch located on the hot plate, the bimetallic thermostat used to regulate the

temperature, or both.

Normally, these two spark sources are located in the lower part of the hot

plate in a region where any heavier-than-air and possibly flammable vapors

evolving from a boiling liquid on the hot plate would tend to accumulate.

Hot Plates

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Heating mantles heat round-bottom flasks, reaction kettles, and related

reaction vessels.

These mantles enclose a heating element in layers of fiber glass cloth.

As long as the fiberglass coating is not worn or broken and no water or other

chemicals are spilled into the mantle heating mantles pose minimal shock

hazard.

Always use heating mantles with a variable autotransformer to control the

input voltage.

Never plug them directly into a 110-V line. Higher voltages will cause a

mantle to overheat, melting the fiberglass insulation and exposing the bare

heating element.

Heating Mantles

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Electrically heated oil baths small or irregularly shaped vessels or to

maintain a constant temperature.

For ≤ 200 °C, a saturated paraffin oil is often used;

For ≥ 300 °C, a silicone oil should be used.

Care must be taken with hot oil baths not to generate smoke or have the oil

burst into flames from overheating.

When using oil, salt, or sand baths, take care not to spill water and other

volatile substances into the baths. Such an accident can splatter hot material

over a wide area and cause serious injuries.

Oil, Salt, or Sand Baths

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Always monitor an oil bath by using a thermometer or other thermal sensing

device to ensure that its temperature does not exceed the flash point of the oil

being used.

For the same reason, fit oil baths (left unattended ) with thermal-sensing

devices that turn off the electric power if the bath overheats.

Molten salt baths, like hot oil baths, offer the advantages of good heat transfer,

commonly have a higher operating range (e.g., 200 to 425 °C), and may have a

high thermal stability (e.g., 540 °C).

Care must be taken to keep salt baths dry, because they are hygroscopic, a

property that can cause hazardous popping and splattering if the absorbed water

vaporizes during heating.

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Hot air baths:-

useful heating devices,

electrically heated,

frequently used to heat small or irregularly shaped vessels.

constructed from metal, ceramic, or, less desirably, glass vessels

low heat capacity

• Tube furnaces are often used for high-temperature reactions under reduced

pressure. The proper choice of glassware or metal tubes and joints is required,

and the procedures should conform to safe practice with electrical equipment

and evacuated apparatus.

Hot Air Baths and Tube Furnaces

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• Laboratory heat guns are constructed with a motor-driven fan that blows air

over an electrically heated filament.

• They are frequently used to dry glassware or to heat the upper parts of a

distillation apparatus during distillation of high-boiling point materials.

• Heat guns almost always pose a serious spark hazard.

• Never use them near open containers of flammable liquids, in environments

where appreciable concentrations of flammable vapors may be present, or in

laboratory chemical hoods used to remove flammable vapors.

Heat Guns

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Air-conditioning is a process of controlling the air temperature, relative

humidity, ventilation, air movement and air cleanliness of a given space in

order to provide the occupants with a comfortable indoor temperature.

One of the costliest items in a laboratory construction project is the air

conditioning system.

Labs need more air than almost any other type of facility and supplying that

air can be expensive.

Two Major Types of Systems:

1.Constant Volume (CV)

2.Variable Air Volume (VAV)

Air conditioning systems

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Constant Volume System

It exhausts a constant amount (volume) of air through the lab fume hoods while

at the same time supplying a constant volume of air into the laboratory.

The amount of air exhausted and supplied is constant.

Advantages:

The constant volume system is simple (to design, install and maintain).

The start-up and testing, installation, and maintenance can be performed by

conventional experienced HVAC contractors.

Since all hoods will be in operation at all times and that they will be exhausting

at a constant rate it is likely that the equipment specified for a CV system is of

sufficient size to provide enough air for a safe, comfortable lab.

The initial cost of a CV system is typically lower than a VAV system requires

more controls and more sophisticated equipment they tend to be more expensive.

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Variable Air Volume Systems

Variable Air Volume (VAV) systems vary the amount of air being exhausted and

supplied to a lab based upon the usage of the fume hoods.

Systems utilize a sensing device built into the side wall of the hood to measure

the air volume drawn into the hood.

As the volume increases the sensor activates and increases the exhaust. A

decrease in the air volume results in a reduction of the exhaust.

Advantages:

Cost savings resulting from reduced energy consumption. Since the system

exhausts less conditioned air it requires less conditioned air with resulting lower

energy costs.

Reduction in size of the HVAC equipment. distinct advantage if space is at a

premium. A subsequent reduction in equipment cost is also achieved.

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When considering and selecting an air conditioning system, the designer must

evaluate the following factors:

Building location, surrounding environment and external climate.

Uses and functional requirements of the building

Client’s budget, investment policy and expected quality of service

System qualities– e.g. aesthetics, life, reliability and maintainability. However

for the present work unitary air conditioning system is selected.

Energy consumption – for both economic and environment reasons

Air Conditioning System Selection

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It is required to promote and maintain laboratory safety and protection to life

and property.

Items such as fume containment, worker safety, proper cleanliness through

pressure relationships, filtration, air changes per hour (ACH), point of fume

capture, temperature, and Relative humidity requirements are elements

necessary to design the ventilation system depending on the laboratory type.

When working in a required clean environment such as when mixing

medications (pharmacy) or working with infectious bacteria (research), airflow

direction and air cleanliness are requirements.

Ventilation

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Laboratory fume hoods are a type of specialized local exhaust that is

designed to isolate and remove gases, vapours, and particles from laboratory

sources and limit exposure to the user.

The location of the fume hood with respect to open windows, doorways, and

personnel traffic directly influences the containment ability of the hood.

Fume hoods should not be located adjacent to a single means of access to an

exit.

A fire hazard or chemical release incident, both of which may start in a fume

hood, can block an exit rendering it impassable.

A fire or explosion in a fume hood located adjacent to a path of egress could

trap someone in the lab.

Hoods should be located more than 10 feet from any door or doorway.

Laboratory Fume Hoods

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Architectural features and their recommended distance from fume hoods.

Drying ovens or drying cabinets shall not be installed underneath fume hoods.

The heat from drying ovens increases the risk of volatilization of chemicals

inside the fume hood, particularly chemical solvents and may increase the risk

of explosions or fires.

In addition, heat transfer to the fume hood may affect the functionality of the

fume hood

Architectural Feature Minimum Distance from Hood (feet)

Pedestrian Walkways 4

Opposite Laboratory Bench 5

Opposite Laboratory Fume Hood 10

Adjoining Laboratory Fume Hood

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Opposing Wall 7

Adjoining Wall 1

Doorway 10

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• Laboratory Design Guidelines-University of North Carolina, USA

Designing and planning of laboratories (2009)

Laboratory Design and Construction Guidelines (2010)-University of South

Carolina, USA

International Journal of Application or Innovation in Engineering &

Management (IJAIEM), Volume 2, Issue 9, September 2013 Page 287

Forensic Laboratories: Handbook for Facility Planning, Design,

Construction, and Moving

References

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