1. A sizing guide for assisting in the determination of an appropriate size respirator mask for a user thereof, comprising: a first sizing gap and a second sizing gap, the first sizing gap having a first known width and the second sizing gap having a known width different from the first known width of the first sizing gap, such that comparison of the first sizing gap and the second sizing gap with the length between a first landmark and a second landmark on the face of the user provides an approximation of the appropriate size respirator mask for the user.