Both check and verify that the seal between the mask and skin is maintained, however, the procedures, who administers the test and circumstances when each is used differ. The procedures are detailed earlier in this Quick Tip. The employer is responsible for administering the fit test, and it is done by someone other than the user of the respirator. The user of the respirator performs the user seal check (fit check). The circumstances for performing a fit test are defined by OSHA: prior to first issue of a respirator, when there’s a change in the model, style or size of respirator used, when there’s a physical facial change in the person wearing the mask, and at least annually. The user seal check (fit check) is done each time the mask is put on, even if this occurs several times per day.