Masks for COVID‑19

Wearing a mask correctly and consistently is an effective way to prevent getting and spreading COVID‑19. This document provides information to help you make decisions about the use of masks in your workplace and develop your workplace policies.

COVID‑19 spreads primarily from person-to-person through respiratory droplets created by a person who is infected. Respiratory droplets vary in size from large droplets that fall to the ground rapidly near the person, to smaller droplets, called aerosols, that can remain suspended in the air.

Masks are used to prevent these droplets from getting from one person to another. They can serve two purposes at a workplace:

  • as source control: people wear masks to protect those around them from any virus they may breathe out
  • as personal protective equipment (PPE): people wear masks to protect themselves from breathing in any virus that may be in the air around them

Many types of masks can work as both PPE and source control, but not all masks are suitable for both purposes. At minimum, all masks for COVID‑19 should:

  • cover the wearer’s nose, mouth and chin
  • be fixed to the face with straps, ties or elastic — either behind the head or with ear loops

Bandanas, scarves and neck gaiters do not meet these criteria.

To decide whether and how you will use masks in your workplace, you will need to assess all relevant factors in the workplace and local community, including:

  • Are there physical features of your setting, types of interaction or activities that increase the key risk factors for transmission of COVID‑19?
  • How effective are your current control measures at reducing identified risks?
  • What is the level of risk locally (consider current indicators of local COVID‑19 transmission)?

Read the guide to developing a COVID‑19 workplace safety plan to help you understand the risks related to COVID‑19 in your workplace and identify concrete actions you will take to make your workplace safer.

Make sure you follow all public health and occupational health requirements, including under the Occupational Health and Safety Act (OHSA) and any public health orders and local by-laws.

Using masks as source control

Using a mask as source control means wearing a mask to protect other people. This prevents the spread of COVID‑19 and other viruses by acting as a barrier, capturing infectious droplets that the person wearing the mask may be breathing out.

COVID‑19 can be spread by people who do not have any symptoms (called asymptomatic spread). Therefore, it can be a good idea to have people wear a mask even if they do not have any symptoms.

When using masks as source control, you should consider the effectiveness of the mask for that purpose. Masks with unfiltered exhalation valves should not be used in any situation where source control is important.

Universal masking

Masks work best when everyone wears them. Universal masking means having everyone wear masks at all times. This applies regardless of the ability to maintain two metres of distance from others.

Universal masking reduces the amount of virus that may be emitted into the air. It is an important and effective control measure, when indoors and in other shared enclosed spaces such as vehicles and tents. Masking can work even better when combined with effective ventilation.  

If your workplace uses universal masking:

  • ensure you have a policy in place to help protect workers from violence and harassment by members of the public who do not want to wear a mask
  • consider how you will manage spaces where universal masking is not possible, such as in lunchrooms when people are eating

Using masks as personal protective equipment (PPE)

A mask can also be worn to protect the person wearing it. In the workplace, there are legal requirements about use of PPE to protect workers from hazards that are known to be there. A mask can also be worn to protect the wearer even if there is no legal requirement for PPE in the specific situation.

For COVID‑19, masks can help prevent transmission by droplets of all sizes.

A PPE mask for preventing large droplet transmission acts as a barrier to prevent droplets from reaching the mouth and nose of the person wearing the mask. This can be important when people need to come within two metres of others who are not wearing a mask.

Both surgical/procedure masks (approved by ASTM or an equivalent standard) and respirators can effectively serve this purpose. Respirators include those approved by NIOSH or CSA (such as an N95 filtering facepiece) or under international standards (such as KN95 and KF94 masks).

A PPE mask for preventing aerosol (small droplet) transmission filters aerosols from the air that is being inhaled by the wearer.

When there is known to be exposure to COVID‑19, such as interaction with a symptomatic person or individuals who have tested positive for COVID‑19, the PPE likely includes an appropriate fit-tested respirator (such as a NIOSH-approved N95 filtering facepiece).

There is some evidence that a well-fitting surgical/procedure mask may provide some protection to a wearer in a situation where the risk of aerosol exposure is fairly low, such as in spaces where universal masking is in place or in well ventilated spaces which are not crowded.

A respirator will provide better protection in situations where a person may be exposed to high amounts of COVID‑19 in the air.

As PPE, masks prevent transmission through the nose and mouth. While these are important entry points through which people can get infected with COVID‑19, other PPE such as eye protection may be required to reduce the risk to workers.

To determine what type of PPE can help to control COVID‑19 risks in your workplace, you will have to assess relevant factors including the effectiveness of other controls you already use.

Combining masking with other controls

Masks work alongside other control measures to help reduce the risk in your workplace.

Consider how to:

  • prevent the virus from getting into the air by:
    • using source control masking
    • reducing the number of people onsite
    • screening workers, for example for symptoms and exposures
  • reduce the potential for virus particles to accumulate or reach other people by:
    • improving ventilation
    • having people spend less time indoors
    • promoting physical distancing
    • protecting workers from any infectious particles that may be present by using more protective masks
  • reduce susceptibility to illness and infection through vaccination

Consider what other controls are in place when deciding how to use masking in your workplace. There may be situations where masking is needed to comply with your duty under the OHSA to take every precaution reasonable in the circumstances for the protection of workers.

Selecting masks

Masks are used to prevent infectious droplets from getting through. Not all masks are equally good at this. Mask qualities that affect performance and effectiveness include:

  • how well the mask prevents particles from getting in and out from around the edges of the mask (quality of fit) and through the mask (level of filtration)
  • your workers’ ability to wear it when needed, for as long as needed (for example, breathability, comfort and durability)

A mask that fits better and filters better will work better for both source control and protecting the wearer.

Improving the fit of masks

A surgical/procedure mask or respirator can be used to:

  • protect the wearer from infectious droplets
  • reduce the amount of virus the wearer would breathe into the surrounding air

Having a well-fitting mask reduces the amount of air which gets around the sides of the mask, and therefore the amount of unfiltered air which is breathed in and the amount breathed out that enters the surrounding air.

There are multiple ways of improving the fit of a mask, including:

  • trying multiple types of masks/respirators to find the best fit and comfort
    • this could be part of a formal fit test (for respirators) or based on subjective experience of the wearer
  • placing a mask brace or fitter over a surgical/procedure mask
  • wearing a cloth mask over a surgical/procedure mask (do not combine two disposable masks or wear a cloth mask over a respirator)
  • pulling the mask tighter by connecting the ear loops behind the head or by shortening the ear loops (for ear loop masks or respirators)

Fit testing of respirators

A fit test is done to:

  • check that a respirator fits closely against the person’s face
  • help ensure that the respirator can provide the proper level of protection

Fit testing cannot be performed on surgical/procedure masks or cloth masks, as they are not designed to seal to the wearer’s face.

Where an employer determines that a tight-fitting respirator (such as a disposable N95 filtering facepiece) is required as PPE to protect the wearer from a specific hazard, the respirator must be fit tested to the worker. An employer or individual can always choose to use fit testing to optimize fit.

Fit testing must be done by someone trained in the procedure. They must use the proper equipment for the type of test they are performing. They can perform two different types of test:

  • a qualitative fit test is based on the wearer’s ability to taste a sweet or bitter solution at very low levels
  • a quantitative fit test uses a specialized machine to measure the particles inside and outside the mask

Find more information about fit testing.

Workers required to wear respiratory protection need to:

  • be trained in the proper use and care of all required PPE, including respirators
  • conduct positive and negative pressure user seal checks before every use (this is done each time a respirator is put on to check it is properly sealed to the face)

Choosing masks with better filtration

Masks are made from different materials. Some materials are better able to filter – that is, to stop and trap – airborne particles (such as viruses and bacteria). How well they are able to do this is known as filtration efficiency.

Masks can be rated on their filtration efficiency. The particulate filtration efficiency (PFE) is a measure of how well the material that a mask is made of can filter particles of the size tested. A higher number means the mask is better at filtering those particles. You can get information about mask filtration from performance standards such as NIOSH, CSA and ASTM International standards. These standards also provide information on other mask characteristics including breathability and fluid resistance.

If air is coming into or leaving the mask through gaps around the edges, that air is not being filtered. Therefore, how well the mask fits affects how well the mask filters the air overall. Masks designed as respiratory protection provide the highest level of protection because they combine tight fit and high filtration. Both N95 respirators and level 1 ASTM surgical/procedure masks are made from a material that filters at least 95% of particles, however, because of differences in fit they do not provide the same level of protection to the wearer or to those around them.

A surgical/procedure mask which fits snugly to the wearer’s face will filter more of the air being breathed in and out than a loose-fitting surgical/procedure mask.

A fit-tested respirator will filter more of the air being breathed in and out than a surgical/procedure mask.

Considering breathability and comfort

For workers who must wear a mask for long periods, a more breathable and comfortable mask is more likely to be used consistently and correctly. Workers may need to try multiple masks to find one that is best for long-term wear. A preferred mask should be considered appropriate as long as it provides equal or better protection to one the employer requires.

Overall mask performance

Not all masks work equally well. When choosing what types of mask to use in your workplace to address the risk, you should consider the quality of fit and the level of filtration. Some options for masks, from generally more effective to less effective, may include:

  • respirators which have been fit tested
  • respirators which have not been fit tested 
  • surgical/procedure masks with a mask brace or a cloth mask over a surgical/procedure mask
  • surgical/procedure masks alone
  • cloth masks (three layer) and disposable masks which do not meet the standards of a surgical/procedure mask

Some individuals may prefer to wear a mask that they supply. If a mask meets or exceeds the performance of any mask required by your policies or of any mask you provide, its use should be permitted. This means that when your workplace policy calls for the use of surgical/procedure masks either as PPE for large droplet transmission or as source control, respirators may be considered an appropriate alternative, whether fit tested or not.

Evidence does not support the use of other face coverings (such as bandanas or neck gaiters) as PPE or source control.

Using masks properly

Make sure workers are trained on the type of mask they are using and its care, use and limitations. Workers should understand whether they are using masks as source control, PPE or both.

How effective masking will be at preventing transmission in your workplace depends on:

  • the type of mask(s) used
  • masks being worn properly and consistently by everyone

Masks must not introduce any new health or safety hazards into the workplace, such as the masks getting caught in machinery.

Accessibility and accommodations

Some people may need to wear a more protective mask because of a health condition. Alternatively, not all people are able to wear masks, for example, because of a health condition. Develop a policy to address these situations before they arise.

Accommodations for someone who cannot wear a mask must not result in reduced protection for workers. Employers may need to implement other control measures to:

  • protect workers in situations where individuals around them cannot wear masks
  • maintain protection for workers who cannot wear masks

For people who need to have their faces seen, such as for lip reading, masks with clear panels are available for source control and PPE. Like all masks, these should securely cover the nose and mouth and fit closely to the face without gaps. If you choose to use a mask with clear panels as PPE, ensure that the mask is designed to meet this purpose.

Protecting workers

Under the OHSA, employers must take every precaution reasonable in the circumstances to protect the health and safety of workers. This includes protecting workers from hazards posed by infectious diseases.

As part of fulfilling these obligations, you will need to:

  • assess your workplace to determine what you need to do to protect the health and safety of your workers, including how to minimize the risk of transmission of COVID‑19
  • implement appropriate control measures which meet or exceed any minimum standards

Make sure you also follow any public health orders and local by-laws.

This document provides information to help you make decisions about the use of masks in your workplace. It does not replace the OHSA and its regulations and should not be used as or considered legal advice. Health and safety inspectors apply the law based on the facts in the workplace.