Masks: What should I wear and when?


A tiny bit of science

When a person coughs, sneezes, talks loudly, shouts or sings and is not wearing a mask they emit large droplets of secretions as well as much smaller droplets called aerosols. Both can contain the COVID-19 virus if that person is infected.

The larger and heavier droplets drop to the ground within a few feet. The aerosols however can float around for considerable time, and spread over large distances, particularly in enclosed spaces with no currents of air to blow them away. Thus, aerosols are a big danger.

This tells us 3 things:

  1. An appropriate mask worn by the cougher/sneezer should reduce the numbers of both large droplets and aerosols released, and an appropriate mask worn by someone nearby should reduce the inhalation of both of these.
  2. Maintaining distance is important, but this mainly protects against large droplets, not aerosols – a crucial point.
  3. Good ventilation inside a building or the fresh air outside are important in minimizing exposure to the aerosols.

Masks – general

There is still confusion regarding the ideal mask. Viewing the CBC Marketplace evaluation of masks is strongly recommended (please click underlined section to access the article).

  • Almost any mask e.g. made from an old T shirt or scraps of cloth will filter out large droplets but not aerosols.
  • Whatever mask is worn must cover the nose and mouth. Shape the pliable metal piece snugly around the contour of your upper nose and try to get as snug a fit as possible over the rest of your face and chin.
  • Mask usage must be combined with other key elements in the prevention of viral spread – distancing, good ventilation, limiting time of exposure to infectious environments, and hand sanitation.

Masks – specific

It follows that a good mask that focuses particularly on aerosol blocking should be made by a professional company whose products have been subjected to quality control processes.

N95 masks (also known as respirators)

These are used by medical personnel and some are available to the public. We recommend quality versions of these as the best choice. They are made from materials that will filter out 95% of the aerosol-containing viruses. BUT BUYER BEWARE: There are good and bad N95’s out there. Those labelled KN95 sold in some stores locally are made in China. Some time ago Sweden ordered a large consignment of Chinese-made N95s, found the quality to be lacking, and destroyed them all. However, other manufacturers in China may have higher standards.

By contrast, hospitals here are using N95s made mainly by 3M in the USA so we can assume that these are up to standard. A company (VITACORE) in Burnaby makes CAN95s which have been authorized by Health Canada for use by health professionals and are said to out-perform other N95 masks. They make an almost identical mask, the CANe95, which is available to the public. It does not carry the authorization of Health Canada, presumably because this is not required for consumer masks, but our understanding is that the CANe95, like the CAN95, is a high quality mask. They cost $5 each – see addendum below.

It is said that N95s should not be re-used.  Washing them in any way is almost certain to damage their constituent materials. Others say that they can be re-used, NOT by washing, but leaving them at room temperature for 24 hours which inactivates the virus. Higher temperatures e.g. via a toaster-oven speeds this up, but we have no information about temperatures and timing. Do not put them in a microwave oven as they contain a piece of metal. Thus, if you opt for an N95, buy at least two.

Surgical masks

These are the commonly seen medium-pale blue masks that are usually made from 3 layers of material. Since they are worn by many hospital workers, they must be good – right? Well, there are two problems: One is that identical masks are sold in hardware and other stores but the fine print reads “for general or industrial use; not for medical use”, so who knows what they are made of and how effective for filtering droplets and aerosols they are? (AGAIN BUYER BEWARE).

The filtration properties of certified medical grade surgical masks are very good. A drawback is that they are not tight fitting and so allow some spillage of droplets and aerosols. They are not reusable but are relatively cheap. This type of mask made by VITACORE is approved by Health Canada and is RECOMMENDED as our second choice. These cost $2.50 each – see addendum below.

“Locally made” and commercial “consumer” cloth masks

Enthusiastic and well-meaning Toms, Dicks and Marys with sewing machines started making masks (often with 2 layers of material) early in the pandemic. These are NOT RECOMMENDED because one usually has no idea of the type or quality of the cloth.

The weave and type of cloth is crucial regarding blocking droplets, let alone aerosols. 100% cotton with a thread count of 600 or above is what is recommended, but this information is seldom included in the labelling of “100% cotton” masks.

An additional issue is that of the number of layers of material a cloth mask should have: Health Canada now recommends that masks should consist of 3 layers. The outer and inner should be of tightly woven cotton or linen – these catch the large droplets. A layer of non-woven polypropylene fabric (a plastic product) is sandwiched in-between – this catches the aerosols. (This material is also used in N95s and good quality surgical masks).

However, recent trips to large retail outlets found mainly 2-layer cloth masks inadequately labelled re: the cloth, or 3-layer masks of allegedly 100% cotton (but with no thread count), and none consisting of the sandwiched-in polypropylene fabric. All were made offshore.

But if you buy or own one of these two-layer cloth masks you can improve its efficiency re: aerosols by inserting a layer of non-woven polypropylene fabric between them. Amazon sells this but so far we have not found a reliable local source.

Bottom Line: Commercially made masks are RECOMMENDED only if made with high quality cloth plus a non-woven polypropylene layer. They fit better than a medical grade surgical mask, and so are possibly better. This ties for a 2nd place RECOMMENDATION. 

The singers mask

This has been designed specifically for singers who are not performing in the “privacy” of Zoom, e.g. they are attending an in-person singing lesson or a small performance (currently not allowed in most places in Canada). Check out Room to Sing.

Masks with exhalation valves

They protect the wearer but no one else. NOT RECOMMENDED.

Bandanas, single layer polyester gaiter mask (popular with athletes), neck warmers, scarves


Plastic face shields

These provide inferior protection compared with a good mask correctly worn. NOT RECOMMENDED.

When and where to wear your mask?

  • Absolutely when inside any building where there are or have been other persons within the last 3 or 4 hours.
  • Since aerosols build up when there is inadequate ventilation, get out of that building as soon as you can.
  • No eating and drinking in pubs and restaurants where you have to take off your mask and where ventilation may be inadequate. Outdoor patios may be OK.
  • Walking in the street: Debatable – depends how many other pedestrians.
  • Parks: Can go without your mask unless there are many persons around and distancing is impossible.
  • Cars: If the passenger is not in your bubble, both should wear masks, keep the windows open and the trip as short as possible.


Vitacore products and types of masks can be seen and ordered on-line at:

Prepared by:

Dr. John Stewart, Jan Nordin PhD, Dr. Nis Schmidt: 14 Nov 2020. Thanks to input from other choir members.