If the workload is heavy it might be a good alternative to select a fan-assisted respiratory protection device. The system consists of a face section, a hose between the face section and the waist-carried fan and a suitable filter. Depending on the contaminant you can choose either a loose-sitting hood or mask that seals against the face. The fan blows air,which is purified by the filter,up into the face section and thereby creates an overpressure area inside it. This effectively blocks any hazardous elements from getting in. Filters must be replaced when they get clogged or saturated.