The two most important considerations when shopping for masks are fit and breathability. An additional layer of filtering in your mask may make it more difficult to breathe through.
If a filter is utilized, it should be sandwiched between the outer layers of the cloth masks for an optimal fit.
To know if your face mask is effective in filtering out particulate, you can check this link.
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There are other important things to keep in mind while shopping for masks: There are five criteria to consider when looking for a mask:
They must fit snugly (but comfortably) against your face
They must be secured with ties or ear loops
They must include multiple layers of fabric
They must allow for breathing without restriction
They must be washable without damage or shape change
A recent study found the quality of fabric plays a role in how effective a cloth mask is at filtering out particulate. The most effective design, according to the study, was a dual-layer mask that included both a heavyweight cotton layer and a lighter cotton or silk layer.