Fit, Fit, and Fit! Once you're comparing respirator masks in the >95% filtration category, it's most important to find one that doesn't leak air around its perimeter while you're wearing it. Finding a good fit takes some trial and error to determine which one works on your head and face. Consider trying our sample kits to help find your fit. On a side note, we also think breathability is very important. That's why we only carry the most breathable respirators in Canada.