If you have a tight-fitting face mask, like an N95/99/100, FFP3/2/1, or elastomeric respirator, you can check the fit of your mask using a qualitative or quantitative fit test or by performing a fit check.
If you have a tight-fitting face mask, like an N95/99/100, FFP3/2/1, or elastomeric respirator, you can check the fit of your mask using a qualitative or quantitative fit test or by performing a fit check. Fit checks have become a popular way to check mask fit since COVID-19, because it has become costly and difficult for hospitals and companies to obtain the supplies needed for qualitative or quantitative fit testing. However, our research indicates that fit checks are unreliable.
The more reliable methods of checking a mask for fit are by qualitative or quantitative testing. Quantitative fit testing is highly reliable but requires equipment costing tens of thousands of dollars. Qualitative fit testing is a less reliable but less expensive method of assessing fit.
In a qualitative fit test, a subject is exposed to a substance, such as sodium saccharine, while wearing the tight-fitting face mask. If the subject can taste (or in some cases smell) the solution, the mask is considered to not have a good fit. You can purchase qualitative fit tests online, but since COVID-19 most suppliers are out of stock of the necessary equipment.
There is no NIOSH approved way to perform a qualitative fit check without a commercial kit. However, for those who feel it is worth the risk, we have devised a way to perform a qualitative fit check with a few inexpensive components. We would like to stress that the safety of this method has not been ascertained. Please move forward with this method at your own risk!