Respirator Selection Tool

Introduction

This tool is for the selection of respirators for protection from bioaerosols and is for use in conjunction with CSA Z94.4, Selection, use, and care of respirators (2011 and 2018 editions).

This tool is intended for use by a qualified person following application of established occupational health and safety principles and a risk assessment for the specific exposure situations under consideration.

The selection process addresses a single workplace environment and activity causing exposure. Changes in workplace environment or activity require the tool to be used again.

A report can be generated in which the user can complete other details about the exposure situation along with the guidance outputs for future reference.

CSA Group always strives to provide up to date and accurate services, tools, and information. However, no representation or warranty, expressed or implied, is made that the Respirator Selection Tool (the “Tool”) meets your specific needs and any reliance on the quality, reliability, timeliness, usefulness, sufficiency and accuracy of information provided by and recommendations made by this Tool, after inputs are made by you, is at your own risk. The Tool, including any documentation, publications, software programs or code is furnished on an "as-is" basis, and the use of the Tool, is directed to those who have the appropriate degree of knowledge and experience to use and apply the Tool. Please contact CSA Group for more information about this Tool and our services.

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This tool is based on a control banding method which uses a semi-quantitative assessment of factors as inputs into a decision process to provide a recommended level of respiratory protection (output), from which selection of appropriate types of respirators can be made.

View CSA Z94.4-18 on the CSA Store

Guidance for hazard assessment for bioaerosols

This is additional guidance from Annex M (adapted from CSA Z94.4-18) for qualified persons responsible for determining levels of risk associated with micro-organisms transmitted by the airborne route in health care environments.

Conditions for airborne transmission

The following conditions must be present for airborne transmission of infection to occur:

Micro-organisms contained in the particles must be capable of remaining viable in the air for a prolonged period of time.
There must be a susceptible host.
The susceptible host must be exposed to a sufficient concentration (infectious dose) of the viable micro-organisms.
The appropriate cell-surface receptors for the micro-organisms are present at the site of exposure.

Probability of airborne exposure

The probability of airborne exposure to a micro-organism contained in a bioaerosol is influenced by several factors:

proximity of the infected source (such as an infectious patient) to the respirator user;
particle sizes of aerosols carrying the infectious micro-organism;
viability of the infectious micro-organism; and
animate and inanimate environment of a room.

Additional routes of transmission

When micro-organisms have additional routes of transmission or a patient is infected with more than one type of micro-organism with multiple routes of transmission, the qualified person takes all routes of transmission into consideration during the risk assessment stage.

If there is also a risk of acquiring the disease by the contact route, the qualified person considers the risk to the user of self-inoculation from contaminated personal protective equipment and to anyone else who might come into contact with that equipment.

Micro-organisms known to be transmitted from human to human by the airborne route

Susceptible workers should use a respirator when caring for a patient, resident, or client with a suspected or confirmed infection caused by any of the following micro-organisms until the patient or environment is deemed no longer to be infectious:

rubeola (measles virus);
monkeypox;
respiratory (pulmonary, laryngeal, pleural) Mycobacterium tuberculosis (also M. africanum, M. bovis). A respirator is also recommended while performing aerosol-generating medical procedures on non-pulmonary lesions infected with Mycobacterium tuberculosis (also M. bovis, M. africanum);
variola virus (smallpox);
vaccinia;
varicella zoster virus (varicella/chickenpox);
varicella zoster virus (disseminated herpes zoster/shingles); and
coronavirus in severe acute respiratory syndrome (SARS CoV2).

Possible human-to-human airborne transmission may occur with aerosol-generating medical procedures

This may be observed for emerging respiratory infections.
Viral hemorrhagic fevers due to Lassa, Crimean-Congo, Ebola, and Marburg viruses could theoretically be transmitted from human to human by the airborne route during aerosol-generating medical procedures.

Steps in hazard assessment for non-infectious (NI) bioaerosols (Risk Group 1)

Note: The qualified person can consult the references below for background information and additional guidance on determining an appropriate risk group classification.

1. Determination of hazard(s)
The nature of the hazard(s) should be determined as follows in order to perform a risk analysis:

Identify which NI bioaerosol(s) are present in the workplace.
Estimate or measure the concentration of the NI bioaerosols.
Determine if there is an applicable health regulation or a substance-specific standard for activities or setting in order to control occupational exposure to NI bioaerosols.
Identify appropriate guidelines specific for activities or setting in order to control occupational exposure to NI bioaerosols.

2. Characterisation of NI bioaerosols

The following factors concerning an operation or process should be taken into consideration to evaluate exposure:

operation or process characteristics as they relate to the release of NI bioaerosols through routine or non-routine procedures;
the length of time, and its impact to worker effective protection for which the respirator is to be used and the work physical demands;
work area layout, work activities, temperature, relative humidity, atmospheric pressure, seasonal variations and maintenance procedures;
materials used, produced, or stored, including raw materials, end-products, by-products, fragments, toxins, and particulate waste products from all varieties of living things; and
non-routine procedures such as emergency repair, shutdown procedures, escape and rescue operations, or potential accidental exposure such as spills or malfunctioning of equipment or processes.

3. Identification of NI bioaerosols by physical state

The physical state for all NI bioaerosols in the workplace should be noted, either as a particle, a liquid, or a solid.

4. Estimate or measure the concentration of NI bioaerosols

An estimate of the airborne concentrations of NI bioaerosols to which workers might be exposed should be conducted by qualified person(s) as follows:

if appropriate, an air sampling and analysis conducted in accordance with recognized occupational hygiene practices;
mathematical modelling or estimating based on the workplace volume; or
experience from similar circumstances and previous situations already documented.

5. Complete the hazard assessment for non-infectious (NI) bioaerosol

Continue to assessment procedures in Clauses 6.5 to 6.7.

Steps in hazard assessment for infectious bioaerosols (Risk Group 2, 3 or 4 respectively) potentially present — Determination of the nature of the potential hazard(s)

The nature of the hazard(s) should be determined as follows in order to perform a risk analysis. Identify which infectious biological aerosol(s) [airborne micro-organism(s)] are present for the work activities. Document and take into account available data on the following elements:

which micro-organism(s) is potentially present and their potential infectious or other adverse effect(s) if inhaled;
Note: When there are multiple types of micro-organisms, focus on the most hazardous ones (i.e. highest risk group).
generation rate of potentially infectious bioaerosol(s) of work activities, frequency of exposure and portal(s) of exit (aerosolization processes e.g., coughing, sneezing, potential re-aerosolization);
what is known or unknown regarding the potential capacity of micro-organism(s) to survive and maintain capacity for infection in an aerosol in a work environment through extended period of time and knowledge of environmental factors which may affect this capacity;
behaviour of infectious biological aerosol(s) from source (e.g., human, animal) to respiratory zone of worker(s) for work activity being assessed;
Note: This behaviour is related to the particles’ sizes, association with particles, source proximity, temperature, relative humidity, UV light and technical attenuation controls (e.g. ventilation conception, and work area layout).
estimate or measure the concentration of the potentially infectious bioaerosols;
determine if there is an applicable health regulation or a substance-specific standard for activities or setting in order to control occupational exposure to infectious bioaerosols; and
identify appropriate guidelines specific for activities or setting in order to control occupational exposure to infectious bioaerosols.

Notes:

Some stakeholders might want to include an assessment of worker’s individual susceptibility (e.g., previous immunization, immune system competency, vaccination and efficiency of vaccination) by a qualified person. However, ethical, scientific, legal, and social considerations should be taken into account.
References provided below may be consulted by qualified person(s) for background information and additional guidance on determining an appropriate risk group classification.

Additional References

The following references are provided to assist a qualified person in selecting an appropriate risk group classification for bioaerosols.