How well do different mask filter materials protect you?

Testing to Standards

It’s probably safe to say that the global demand for respiratory protective devices has never been higher. Manufacturers of devices such as surgical masks and N95 respirators have been increasing their production as quickly as they can, but are not yet able to keep up with the global need. Consequently, a large demand has sprung up for masks and other face coverings to fill this gap. These masks may be made of fabric or other materials, and may be commercially manufactured or made at home.

But how well do these alternative masks protect the person wearing them? The protection provided by a N95 respirator or other regulated device is well-characterized, because such devices are tested according to very specific standards. Conducting testing in accordance with the standards is critical in order to be able to compare results. This is because working with aerosols is complex:

• filters do not equally capture particles of different sizes
• the size-capture relationship changes from one material to another
• depending upon their design, aerosol detectors may use different physical properties to detect particles

Due to this complexity, the best way to ‘compare apples to apples’ is to test materials often used in homemade masks using the same standardized method that is used for N95 respirators. This is the TSI 8130A Automated Filter Tester.

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