Fit testing should be carried out on initial selection or, at least, before an individual uses the respirator in a hazardous environment. If an un-tested mask is in use, or if an operative using tight-fitting RPE has not had a fit test, the relevant test should be carried out immediately. Fit testing should be repeated at regular intervals, determined through company policy and risk assessment, and when:

•  the wearer gains or loses a significant amount of weight.
•  the wearer undergoes major dental work, facial surgery, or sustains a facial injury
•  there is a change in respirator type or size.