The Public Health Agency of Canada (PHAC) is currently recommending medical masks to the following groups:
The PHAC recommendation seems to implicitly discourage the use of non-medical cloth masks for these groups.
When choosing a mask, there are three main categories to choose from, non-medical cloth masks, medical masks and respirators. As non-medical cloth masks are not required to conform to any standard and are often single layer, the protection they offer is generally inferior to that of medical masks and respirators. Also, particulate filtration efficacy of non-medical cloth masks is often highly variable from one product to the next, without any standardized comparison possible. Medical masks and respirators provide superior and standardized protection against Covid-19 as compared to non-medical cloth masks. Given the current PHAC recommendations SafeTMed does not sell any non-medical masks.
The terms medical mask and surgical mask are generally used interchangeably.
Both medical masks and respirators sold in Canada have to conform to standards, but the standards set for respirators are generally more stringent. A respirator is designed to achieve a very close fit to your face and has very efficient filtration of airborne particles. A medical mask is looser-fitting facial device with less efficient filtration of airborne particles, although it still offers significant protection against Covid-19.
The American Society for Testing and Materials (ASTM) has published the ASTM F2100 standard for medical masks based on increasing standards of filtration efficacy at different particle sizes, differential pressure resistance (or breathability), fluid resistance and flammability. The ASTM F2100 specification has three levels within it. ASTM level 3 masks are the highest performing with the best particulate filtration efficacy and the best fluid resistance. However, ASTM level 2 and level 3 masks differ only in their fluid resistance. ASTM level 1 masks offer ≥ 95% filtration efficacy at both 3 μm and 0.1 μm particle sizes, whereas ASTM level 2 and 3 masks are rated at ≥ 98% for each. Note that this particulate filtration efficacy is measured only for the material and does not take into account the fit to a wearer’s face. This data is summarized in the table below:
|ASTM Level 1||ASTM Level 2||ASTM Level 3|
|Filtration 3 μm particles||≥ 95%||≥ 98%||≥ 98%|
|Diff. pressure (mmH2O/cm2)||< 5.0||< 6.0||< 6.0|
|Filtration 0.1 μm particles||≥ 95%||≥ 98%||≥ 98%|
|Synthetic blood resistance (mmHg)||80||120||160|
|Flammability||Class 1||Class 1||Class 1|
An ASTM level 2 medical mask is an excellent choice for people where for whom the likelihood of exposure to fluids is negligible. If fluid exposure is possible or probable, ASTM level 3 is the preferred choice of the medical mask categories. ASTM level 1 masks offer slightly inferior particulate filtration efficacy and can be selected if cost is a primary consideration.
Properly worn and fitted N95 masks offer better protection than any ASTM F2100-rated medical masks. The key explanation for this is that the testing standards for each are quite different. While the ASTM F2100 testing only measures the filtration efficacy of the material itself, the N95 standard evaluates the material and the fit. A hypothetical material with a 100% particle filtration efficacy would be useless if the poor fit of the device allowed massive air flow on either side of the mask.
The ASTM F2100 specification clearly states that it “only evaluates the materials used in the construction of the medical face mask, and not the seal." The integrity of the seal to the wearer's face is not evaluated by ASTM testing, so this information is not captured. N95 respirators, however, are designed to minimize gaps and create a tight seal between the wearer’s face and the outside world. When correctly fitted, an N95 mask achieves a filtration efficiency practically impossible to achieve with ASTM level 3 medical masks. N95 masks must have material with high filtration efficacy and excellent facial seal to gain N95 certification.
A well-fitted N95 respirator offers superior protection than even an ASTM level 3 medical mask and should be selected by those who are at very high risk of exposure to COVID-19 because of their living situation or are at very high risk of more severe disease or outcomes if they get COVID-19 due to their personal circumstances such as age and prior health conditions.
Most medical masks and respirators are rated for single use, however if not visibly soiled, wet or broken, these can be worn many consecutive hours.
N95s and ASTM F2100-rated masks are designed and rated for single use. Although during the crisis conditions of early 2020 re-use and extended use of these devices was tolerated, this was never intended by manufacturers. Given that supply has mostly caught up with demand, the original recommendations are to be favored, that is – single use of respirators and medical masks.
Medical masks and respirators should never be washed as this can destroy the filtration efficacy.
Non-medical cloth masks are washable and reusable, however, they offer distinctly inferior protection when compared to N95s respirators and ASTM F2100-rated medical masks. SafeTMed does not sell any non-medical masks, so none of the products you find on this site are washable nor rated for multiple uses. The Public Health Agency of Canada is currently recommending medical masks for at-risk populations, implicitly discouraging the use of non-medical cloth masks.
Yes, a medical mask or a respirator can offer what’s known as “source control,” and keep the virus from infecting others. It’s recommended to wear a medical mask or respirator if you have tested positive for or have symptoms of Covid-19.
No, properly worn approved masks do not cause low oxygen levels. A study in the Journal of the American Medical Association published in 2020 confirmed what many doctors already took for granted, namely that face masks do not impact oxygenation.