Quantitative fit testing techniques and regulations for tight-fitting respirators: current methods measuring aerosol or air leakage, and new developments.
Han-H; Willeke-K; Colton-CE
Am Ind Hyg Assoc J 1997 Mar; 58(3):219-228
Current qualitative fit testing techniques and regulations for tight fitting respirators were discussed. The general principles of qualitative (QLFTs) and quantitative respirator fit tests (QNFTs) were described. QLFTs involve introducing the challenge agent into the area around the respirator while it is worn. A subjective fit determination is made by the wearer depending on whether or not the agent can be detected by odor, taste, or nose or throat irritation. The QNFT method involves wearing the respirator in a relatively stable test atmosphere, usually containing aerosols. The adequacy of respirator fit is determined by measuring the aerosol concentrations inside and outside the facepiece of the respirator while the wearer performs several head and mouth movements simulating work situations. During the tests, the filters used in the respirator are of the high efficiency particulate air (HEPA) type so that any aerosol particles measured inside the facepiece can be assumed to have penetrated through the respirator face seal and not through the filter. Problems associated with performing QNFTs on filtering facepiece respirators originate from the fact that the filters cannot be replaced with HEPA filters. Under the conditions, it cannot be readily determined whether aerosol particles in the facepiece came from a leak or through the filters. Specific QNFT methods for air purifying respirators with replaceable filters were reviewed. These are based on detecting faceseal leakage from measurements of aerosol penetration into the facepiece or by measuring leak flows directly inside the facepiece. Leak flow methods are based on placing the respirator under negative pressure. QNFT methods for respirators with nonHEPA filter filtering facepieces were discussed. These have been based on measuring the degree of penetration of large or small particles at low flow rates. A more recent method based on monitoring pulsations caused by pulsating volume flows into the respirator has been found useful for poorly fitting respirators. QNFTs for positive pressure respirators were summarized. Standards and regulations governing QNFTs were discussed.
NIOSH-Publication; NIOSH-Grant; Respiratory-protective-equipment; Equipment-reliability; Laboratory-testing; Aerosol-particles; Air-flow; Legislation; Quality-standards;
Author Keywords: aerosol leakage; air leakage; fit testing; respirator; respiratory protection
Environmental Health University of Cincinnati 3223 Eden Ave Cincinnati, OH 45267-0056
American Industrial Hygiene Association Journal
University of Cincinnati, Cincinnati, Ohio