OHS Canada Magazine

How to perform a proper N95 fit test

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April 17, 2020
By OHS Canada

Hazmat Health & Safety Occupational Hygiene Coronavirus COVID-19 Fit Testing Masks Pandemic Respirators

Employees requiring respirators must be properly fit tested

A respirator fit test is crucial to a well-designed respirator protection program. (Khunatorn/Adobe Stock)

By Gloria Bergen

COVID-19 has reached pandemic proportions and the potential for a second wave of the outbreak this fall proves that complacency has no role in the control of new and potentially fatal respiratory diseases.

The leading health organizations all recommend the use of N95 tight-fitting, air-purifying respirators. N95s reduce the exposure to viruses and are also effective when exposed to tuberculosis and other infectious diseases. The prefix ‘N’ refers to not oil resistant, and the respirator will remove 95 per cent of all particles that are at least 0.3 microns in diameter.

The Canadian Standards Association’s Z94.4 standard and provincial regulations for health-care and residential facilities, industrial establishments, and construction sites requires that all workers pass a fit test before wearing a respirator for the first time. Users of tight-fitting respirators require fit testing every two years or sooner.

A corporate respirator protection program must clarify protections available, should another wave of COVID-19 or another infectious disease strike.

Fit-testing program elements

Any comprehensive respirator protection program requires a number of specific elements. Procedures should be available for selecting respirators appropriate for the work being done, for proper use of respirators, for fit testing, and roles and responsibilities of workplace parties.


Additional elements of a program include the following:

  • lists of departments and jobs requiring respirators, as well as a profile and list of respirators required
  • procedures and schedules for storing, inspecting, cleaning, disinfecting and maintaining respirators
  • education of employees regarding potential hazards during routine and emergency situations
  • training of employees on how to properly use, wear, remove and dispose of respirators, as well as the limitations of respirators
  • employee respirator user screening and health surveillance form
  • record keeping — which includes an employee’s name, department, pass or fail of test, brand, model and size of respirator successfully fitted for, date of test and name of tester
  • program effectiveness evaluation procedures.

Protections offered by a comprehensive respirator protection program include properly fit testing for every employee who needs a respirator.

The ‘taste’ test

Upon beginning a fit test, test hoods are placed over employees’ heads. Wearing gloves, the ‘fit tester’ pumps 10 puffs of an aerosolized sensitivity test solution — a dilute version of the fit-test solution (often denatonium benzoate) — into the hood.

Detectable at one part per 20 million, the world’s most bitter substance is a useful tool to stop children from sucking their thumbs or drinking household cleaners.

Because the test is qualitative, the employee will indicate when he tastes the solution. In some cases, workers will tear off their test hoods immediately following the test while others will display a look of disgust. Some do not taste the substance until sufficient concentrations are reached.

The test is given to ensure that employees being fit tested can taste the solution at very low levels, and to determine the concentration of test solution to be maintained during the actual fit test.

Once properly fitted with a respirator, there should be no leaks and, in turn, no taste detected during the fit test.

Employees with compromised respiratory systems (asthma or emphysema) or with chronic heart disease must check with a physician before wearing a respirator. The respirator user screening form provides the opportunity for the user to identify that a prior medical condition exists that may hamper the use of a respirator.

Those employees who have no prior conditions and are able to wear a respirator are administered a bitter test solution or sweet saccharin.

Neither the sweet nor the bitter solution has an odour, so employees are asked to breathe through their mouths for both tests. If an employee doesn’t taste the solution after a maximum of 30 sprays inside the hood, they will require quantitative testing using a calibrated machine.

Common concerns

The industrial hygienist or safety professional performing the fit test should be prepared for a few common problems.

Donning a previously worn test hood may be of concern to some employees — especially during an infectious disease outbreak — and individuals have been known to refuse the test. There are three choices for workers: clean the hood, purchase their own hood or inform their manager that they are refusing to complete the fit test.

Corporate policy should clarify what procedures to follow for many situations — including employees who cannot shave based on religious beliefs. The Canadian Human Rights Act notes that a policy prohibiting beards would constitute discrimination. For everyone else — they need to be clean shaven.

Employees with allergies or breathing difficulties may find it difficult to wear some masks. Those who are allergic to certain fibres often exhibit dermatitis, red skin or complain of itchiness. From field observations, women seem to be more affected, possibly because they wear more lotions and makeup.

The use of a respirator cannot interfere with a worker’s requirement to wear prescription or safety glasses. A worker’s PPE cannot interfere with the ability to use respirator equipment and must maintain an effective seal at all times. The key is to have a respirator that fits the shape of your face and can seal properly.

Ideally, a choice of respirators suitable for various jobs should be available, but the reality is that during a global infectious disease outbreak, not all types of respirators are.

During the current COVID-19 outbreak, many popular disposable N95 respirator brands are out of stock because manufacturers are unable to produce sufficient quantities, even with production revved up and extra production lines in various industries added.

Next steps

Once a respirator has been properly fitted, it is necessary to take note of certain telling comments: “This mask gives me headaches” or “I’m tired all of the time” may be indications of carbon-dioxide (CO2) inhalation.

Some disposable respirator models have an exhalation valve built in that allows for the escape of warm air so as to not fog up the lens of safety or prescription eyewear.

It is acceptable for health-care workers to wear respirators with exhalation valves, except in cases where they are suspect, probable or confirmed cases of COVID-19, or where they must maintain a sterile environment.

Fogging of glasses, goggles and face shields does not indicate that there is a leak in the respirator. Warm air rises and upon exhalation, there is nowhere else for air to go. If this continues to be a problem, a defogging solution may help.

Some employees may be prone to claustrophobia or panic attacks. This will be reviewed using the pre-screening form before you fit test. If so, pay special attention to the subject during the test. Some people may not say a word, but their eyes and body language will tell the truth.

React accordingly.

A respirator fit test is crucial to a well-designed respirator protection program. Qualitative fit tests rely on the subjective taste and reaction of the person being tested, plus the fit tester has no control as to how the user dons the respirator once the test is complete.

You’ve done what you could.

Now it’s the employee’s responsibility to follow what you’ve taught so they can now have confidence that they can protect themselves. Performing a proper positive and negative seal check after each donning will ensure protection.

Now retired, Gloria Bergen assisted North York General Hospital and other health-care facilities through the SARS crisis in 2003, fit testing more than 3,000 employees. She is the former manager of occupational safety at the Princess Margaret Cancer Centre in Toronto and a past occupational health and safety inspector in Ontario. 


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