Dr Catherine Clase (see footnote details)
Joan Fearnley (see footnote details)
Recent developments in the media regarding new COVID variants and double-masking suggestions have led some choral organisations to question and re-evaluate their mask choices. In addition, in November 2020, Health Canada issued the recommendation that masks be made of three layers rather than two as was initially the case. However, many choral organisations invested in masks before this new recommendation.
In this blog post we will review some key considerations of fit and fabrics for future purchases and offer suggestions on how you can update the masks you already have.
Does the mask fit?
It is always important to make sure a mask seals well around the face. Air must flow through the fabric and not around the mask and through the gaps. Any advantage provided by a high filtration fabric will be lost if air isn’t flowing through the fabric. If the mask is not breathable the air will inevitably flow around the mask.
Should we double-mask?
Double-masking is often suggested to address both fit and filtration issues. A well-fitting mask worn over the top of a looser mask (disposable or fabric) could help to provide a better seal. Also layering of masks can improve filtration. Note however, that while layering two two-layer cloth masks would result in a four-layer mask, it will not result in a doubling of mask efficiency. Nevertheless layering will provide some added filtration. Just make sure you can still breathe through all the layers!
If your mask is a well-fitting three-layer mask consistent with Health Canada’s recommendations, double-masking is probably not necessary in most community settings.
Disposable (blue) masks.
Disposable masks are not certified. Consequently, the filtration properties of a particular brand are usually not available. They are also not mentioned in the Health Canada guidance on community masks (though they do mention disposable filters). However, we understand that some authorities and institutions may be requiring disposable masks for some activities. If you are required to use one of these, the addition of a quality, well-fitted, two-layer cloth mask, over the top, could help to provide a better seal for the procedural mask.
What are the recommended fabric layers?
While there are a variety of fabrics that could perform well for regular masks, for singer’s masks we are recommending the following layering, which is consistent with Health Canada’s and the World Health Organization’s recommendations:
Quilter’s cotton: at least 100 threads per inch (clothmasks.ca) and probably 120-180 gsm
In addition to the Health Canada website, a summary of the published evidence for different textiles is available here, and a plain language version, along with other useful information, at the website clothmasks.ca.
Spunbond Non-Woven Polypropylene (SNWPP)
Health Canada recommends a middle layer of spunbond non-woven polypropylene. Researchers at McMaster’s Centre of Excellence in Protective Equipment and Materials think that 70 gsm is likely to be preferable to lighter weights. It can be added as a washable filter or it can be built into the mask. Other middle layers, including woven and non-woven polyester and nylon, are not the same material and they should not be regarded as interchangeable. Non-woven polypropylene was virtually unknown in the home sewing world and was difficult to source when this recommendation was made in November 2020; however, many retailers, large and small, now carry these materials. More information, including information on washing, can be found at clothmasks.ca and in this article in the Conversation.
We already bought Singer’s masks, what should we do?
You will first need to determine what materials were used in your masks. A mask seller would have provided that information to you when the masks were purchased. If this information was lost or not provided you can contact the seller. If your mask materials are not consistent with Health Canada’s (or the World Health Organization) recommendations, the choral organisation should consider purchasing new masks or consider additional layering described below where possible.
Choral organisations that purchased masks in the beginning of the fall season likely purchased two-layer masks or masks with an additional layer of polyester interfacing (used to aid in maintaining the structural integrity of the mask). This was consistent with recommendations at the time.
Because of their construction, many singer’s masks do not have pockets to insert filters as you might find in other community masks. However, it is possible to upgrade a singer’s mask by sewing a simple “shell” made from spunbond non-woven polypropylene 70 gsm that will be inserted directly into the mask. This is a relatively new idea that some sewists have already explored. The anecdotal feedback is positive.
Other singer’s masks are two-layer masks and provide the option of inserting a filter. In this latter case, updating your filters is fairly straightforward provided you make sure it covers the entire area of the mask and seals to the face.You can continue purchasing the filters suggested by the mask seller (disposable or reusable), recognizing that the properties of these filters may not be known, or just cut a polypropylene filter of the right shape and size. If the mask does not seal to the face, air will follow the path of least resistance and flow through the unfiltered fabric.
What is the risk of keeping our old masks?
The short answer is simply “we don’t know”. We do think any mask is better than no mask and we know from mask mandate studies that the masks in use early in the pandemic, imperfect though they were, altered the trajectory of the pandemic when worn. We don’t have direct clinical evidence showing reduced transmission, and no studies comparing different types of community masks. The masks you have may be fine, but we offer these suggestions if you are trying to do everything you can to reduce your personal risk and transmission within your choir.
Consider an ongoing risk assessment and review your rehearsal protocols regularly. Masks are only one part of the equation and are part of a broader strategy that includes: distancing, ventilation, hygiene, screening, length of rehearsals, and the current rate of transmission in your community. And, as always, check with your local public health and institutional requirements.
We wish you many enjoyable hours of safe choral singing.
Dr Catherine Clase:
Physician, epidemiologist, associate professor, McMaster University;
co-lead clothmasks.ca; co-lead Cloth Mask Knowledge Exchange.
Choir director and soprano
Creator of the Mask for Singer’s open-source pattern (YouTube tutorials) and administrator of the Mask for Performers group on Facebook. Contributing author with MakerMask.org
Member of the Cloth Mask Knowledge Exchange
Disclaimer: The views and opinions expressed in this blog post are of the authors and not that of Choral Canada. We are not experts in this field and therefore are not liable for any harm or damages that may come from following this advice.
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Choral Canada is the national voice of the Canadian choral community, representing and uniting a network of conductors, educators, composers, administrators, choral industry leaders, and more than 40,000 choral singers from coast to coast to coast.