When it comes to using respirators it is extremely important to wear it correctly and understand what a "fit test" is so that you are able to protect yourself as effectively as possible.

A fit test is conducted to verify that a KN95, N95, N100 or any other type of respirator is both comfortable, but more importantly fits the wearers face so that it creates a seal. Fit test methods are classified as either qualitative
or quantitative.

A qualitative fit test is a pass/fail test that relies on the
individual’s sense of smell or taste or cough(think what happens when you inhale smoke) to detect a spray or other odorous agent.

A quantitative fit test uses an instrument to numerically measure the effectiveness of the respirator.

So whether you are ordering KN95 or N95 respirator face masks it is important to fit test them properly when you receive them. Ensuring the best experience and usage possible.