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programmeEMERGENCIES

INFECTION PREVENTION AND CONTROL (IPC)

CDC/WHO GLOBAL WEBINAR SERIES

SEVERE ACUTE RESPIRATORY INFECTION (SARI)

TREATMENT FACILITY

VENTILATION SYSTEMS AND MINIMUM REQUIREMENTS

Luca Fontana

environmental toxicologist – epidemiologist

World Health Organization – Emergency Program

Health & Technical team– WHO/WHE/OSL

PRACTICAL IPC CONSIDERATIONS IN THE FIGHT AGAINST COVID-19

23rd July 2020

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Objectives

By the end of this lecture, you will be able to:

• Understand the environment and engineering controls measures within a SARI treatment center

• Explain the ventilation systems and minimum requirements

• Describe Pro and cons of different ventilation systems

Nothing to disclose: I have no financial relationships with commercial entities

producing healthcare-related products and/or services

Crabb, J., Ramage, J., Smith, D.,. IFHE Ventilation Team. Computational Fluid Dynamic

Simulation for Accra COVID’19 Field Hospital. WHO

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SARI treatment center & IPC

Controlling exposures to

hazards is the fundamental

method of protecting

workers, patients and visitors

Most effective

Less effective

Physically remove the hazard

Replace the hazard

Isolate people from the hazard

Change the way people work

Protect the worker with Personal Protective Equipment

CDC, Centers for Disease Control and Prevention. Hierarchy of controls.

Retrieved July 16, 2020, from https://www.cdc.gov/

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Most effective

Less effective

Physically remove the hazard

Replace the hazard

Isolate people from the hazard

Change the way people work

Protect the worker with Personal Protective Equipment

CDC, Centers for Disease Control and Prevention. Hierarchy of controls.

Retrieved July 16, 2020, from https://www.cdc.gov/

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Areas distribution

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Proper staff and patient’s flows

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Finishing and furniture

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Katwa Ebola Treatmente Center, DRC, 2018. Used with permission. Dr Ian Crozier

Technical solution, transparent surfaces

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Technical solution, transparent surfaces & glove box

Sampling box. Time of India

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Ventilation systems and minimum requirements

The purpose of ventilation

is to provide healthy air for

breathing by both diluting

the pollutants originating in

the building and removing

the pollutants from it.

Silenzi, A., WHO. 2020

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Building ventilation has three basic elements:

✓ Ventilation rate — the amount of outdoor air that is provided

into the space, and the quality of the outdoor air;

✓ Airflow direction — the overall airflow direction in a building,

which should be from clean zones to less-clean zones; and

✓ Air distribution or airflow pattern — the air should be

delivered to each part of the space in an efficient manner and

the airborne pollutants generated in each part of the space

should also be removed in an efficient manner.

Crabb, J., Ramage, J., Smith, D.,. IFHE Ventilation Team. Computational Fluid Dynamic

Simulation for Accra COVID’19 Field Hospital.

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There are three methods that may be used to ventilate a building:

Atkinson, J., Chartier, Y., Pessoa-silva, C. L., Jensen, P. & Li, Y. Natural Ventilation for

Infection Control in Health-Care Settings Edited by : WHO Publ. (2009).

Natural ventilation

Natural forces (e.g. winds) drive

outdoor air through the building

openings such as windows, doors,

solar chimneys, wind towers and

trickle ventilators.

Mechanical ventilation

Mechanical fans drive mechanical

ventilation. Fans can either be

installed directly in windows or

walls, or installed in air ducts for

supplying air into, or exhausting

air from, a room.

Hybrid ventilation

Hybrid (mixed-mode) ventilation

relies on natural driving forces to

provide the desired (design) flow

rate. It uses mechanical

ventilation when the natural

ventilation flow rate is too low.

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World Health Organization (WHO). (2020). Infection prevention and control during health care

when COVID-19 is suspected. Who, i, 1–5.

https://apps.who.int/iris/rest/bitstreams/1272420/retrieve

Area Natural Ventilation Mechanical Ventilation

AGPs are NOT performed Average 60 L/s/patient At least 6 air changes per hour (ACH)

AGPs are performed Average 160 L/s/patient Old building:At least 6 air changes per hour (ACH)

New building:At least 12 air changes per hour (ACH)

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Pro and cons of different ventilation systems

Area Mechanical Ventilation Natural Ventilation Hybrid Ventilation

Advantages • Suitable for all climates and weather

• More controlled and comfortable environment

• Smaller range of control of environment by occupants

• Suitable for warm and temperate climates• Lower capital, operational and maintenance• Capable of achieving high ventilation rate• Large range of control of environment by occupants

• Suitable for most climates and weather

• Energy-saving• More flexible

Disadvantages • Expensive to install and maintain

• Reported failure rate in delivering the required outdoor ventilation rate

• Potential for noise from equipment

• Easily affected by outdoor climate and/or occupant’s behaviour

• More difficult to predict, analyse and design• Reduces comfort level of occupants when hot, humid or cold• Inability to establish negative pressure in isolation areas, but

may be provided by proper design; depends on situation• Potential for noise intrusion• High-tech natural ventilation shares some of the limitations

and disadvantages of mechanical ventilation

• May be expensive• May be more

difficult to design

Atkinson, J., Chartier, Y., Pessoa-silva, C. L., Jensen, P. & Li, Y. Natural Ventilation for


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programmeEMERGENCIESAtkinson, J., Chartier, Y., Pessoa-silva, C. L., Jensen, P. & Li, Y. Natural Ventilation for


ACH or l/s

The ventilation flow rate can be referred to as either an absolute ventilation flow rate in l/s or m3/s, or an air-change rate relative to the volume of the space (ACH) .¹

ACH= [ventilation rate (l/s) × 3600 (s/hr)] × 0.001 (m3/s)]/[room volume (m3 )] or

Ventilation rate (l/s) = ACH× room volume (m3) × 1000 (l/m3 )/3600 (s/hr).¹

The steady-state concentration of a pollutant is determined by the pollutant generation rate and the ventilation rate (absolute ventilation flow rate), but not the air-change rate

Therefore, for the purpose of controlling long-term exposure to pollutants, the ventilation rate should be specified, not the air-change rate. ¹

Considering the situation of concentration decay without a constant pollutant source, the decay rate is governed by the air-change rate, not the ventilation rate.

Therefore, for the purpose of reducing the pollutant concentration in a short time after a sudden release of a pollutant, the air-change rate is the most appropriate. ¹


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AGPs are performed Average 160 L/s/patient New building:At least 12 air changes per hour (ACH)

324

m3/h

576

m3/h

Some example: one patient, same room (3x3x3m), different ventilation system

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1.728

m3/h

Some example: three patients, same room (3x3x3m), different ventilation system

324

m3/h

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324

m3/h

2.592

m3/h

Some example: one patient, different rooms (6x6x6m and 3x3x3m), same ventilation system

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Thank you

19 July 2020

Luca Fontana

environmental toxicologist – epidemiologist

World Health Organization – Emergency Program

Health & Technical team– WHO/WHE/OSL

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Bibliography

• World Health Organization (WHO). Infection prevention and control of epidemic- and pandemic-prone acute respiratory infections in health care. WHO

Guidel. 1–156 (2014).

• World Health Organization (WHO). (2020). Infection prevention and control during health care when COVID-19 is suspected. Who, i, 1–5.

https://apps.who.int/iris/rest/bitstreams/1272420/retrieve

• Atkinson, J., Chartier, Y., Pessoa-silva, C. L., Jensen, P. & Li, Y. Natural Ventilation for Infection Control in Health-Care Settings Edited by : WHO Publ.

(2009).

• World Health Organization (WHO). (2020). Severe Acute Respiratory Infections Treatment Centre. World Health Organization Publications, March,

120. World Health Organization

19 July 2020

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