The performance of tight-fitting facepieces depends on achieving a good contact between the wearer’s skin and the face seal of the facepiece. As people come in all sorts of shapes and sizes it is unlikely that one particular type, or size of RPE facepiece, will fit everyone. Inadequate fit will significantly reduce the protection provided to the wearer. Any reduction in protection can put the RPE wearer’s life in danger or may lead to immediate or long-term ill health.