The wearing of respirators is an important means of protecting workers from excessive exposure to air contaminants. A proper-functioning exhalation valve is crucial for an effective respirator. A fast “Respirator Integrity Test” was developed to be used as a quality assurance test before field use of a respirator. The purpose of the test is to assure that no leakage occurs through the exhalation valve nor any other potential leak source in the respirator such as the seal between the respirator body and the air purifying cartridges. If a leak does occur through the respirator, its most likely cause appears to be the exhalation valve. Therefore, the new test method has been compared to a direct “Exhalation Valve Test.” Exhalation valve leakage was measured in both new valves and field-used valves. Leakage through new valves was minimal in most cases, but one brand of new valves was found to leak significantly. Five percent of 67 field-used exhalation valves tested had unsatisfactory leakages indicating that dust or debris on the exhalation valve or valve seat may compromise the proper functioning of the valves. The cleaning of both new and field-used exhalation valves with water caused leakage to decrease significantly, thus supporting the importance of a good respiratory cleaning program for industries.