42 CFR 84.1147 - Silica mist test for dust, fume, and mist respirators; minimum requirements.
(a) Three non-powered respirators will be tested for a period of 312 minutes each at a continuous airflow rate of 32 liters per minute.
(b) The room temperature in the test chamber will be approximately 25 °C.
(c) The test suspension in the test chamber will not be less than 20 nor more than 25 milligrams of silica mist, weighed as silica dust, per cubic meter of air.
(d) Mist will be produced by spraying an aqueous suspension of flint (99 percent free silica), and the flint shall be ground to pass 99 percent through a 270-mesh sieve.
(e) Samples of the test suspension will be taken during each test period for analysis.
(f) The total amount of silica mist unretained in the samples taken during testing, weighed as silica dust, shall not exceed 2.5 milligrams for a non-powered air-purifying respirator.