42 CFR 84.1144 - Silica dust test for dust, fume, and mist respirators; single-use or reusable filters; minimum requirements.
(a) Three non-powered respirators with single-use filters will be tested for periods of 90 minutes each at a continuous airflow rate of 32 liters per minute.
(b) The relative humidity in the test chamber will be 20-80 percent, and the room temperature approximately 25 °C.
(c) The test suspension in the chamber will not be less than 50 nor more than 60 milligrams of flint (99 percent free silica) per cubic meter of air.
(d) The flint in suspension will be ground to pass 99 percent through a 270-mesh sieve.
(e) The particle-size distribution of the test suspension will have a geometric mean of 0.4 to 0.6 micrometer, and the standard geometric deviation will not exceed 2.
(f) The total amount of unretained test suspension in samples taken during testing shall not exceed 1.5 milligrams for a non-powered air-purifying respirator.
(g) Three non-powered respirators with reusable filters will be tested and shall meet the requirements specified in paragraphs (a) through (f) of this section; each filter shall be tested three times: Once as received; once after cleaning; and once after recleaning. The applicant's instructions shall be followed for each cleaning.