(a) Twenty filters of each powered air-purifying particulate respirator design will be tested for filter efficiency against:

(1) A solid sodium chloride particulate aerosol, in accordance with paragraph (d)(1) of this section, if series PAPR100-N approval is requested by the applicant.

(2) A dioctyl phthalate or equivalent liquid particulate aerosol, in accordance with paragraph (d)(2) of this section, if series PAPR100-P approval is requested by the applicant.

(b) Prior to filter efficiency testing of 20 series PAPR100-N filters, the 20 to be tested will be taken out of their packaging and placed in an environment of 85 ±5 percent relative humidity at 38 ±2.5 °C for 25 ±1 hours. Following the pre-conditioning, filters will be sealed in a gas-tight container and tested within 10 hours.

(c) For powered air-purifying particulate respirators with a single filter, filters will be tested at a continuous airflow rate of 85 ±4 liters per minute. Where filters are to be used in pairs, the test-aerosol airflow rate will be 42.5 ±2 liters per minute through each filter.

(d) Filter efficiency test aerosols:

(1) Series PAPR100-N filters:

(i) A sodium chloride or equivalent solid aerosol at 25 ±5 °C and relative humidity of 30 ±10 percent that has been neutralized to the Boltzmann equilibrium state will be used. Each filter will be challenged with a concentration not exceeding 200 mg/m3.

(ii) The sodium chloride test aerosol will have a particle size distribution with count median diameter of 0.075 ±0.020 µm and a standard geometric deviation not exceeding 1.86 at the specified test conditions as determined with a scanning mobility particle sizer or equivalent.

(2) Series PAPR100-P filters:

(i) A neat cold-nebulized dioctyl phthalate (DOP) or equivalent aerosol at 25 ± 5 °C that has been neutralized to the Boltzmann equilibrium state will be used. Each filter will be challenged with a concentration not exceeding 200 mg/m3.

(ii) The DOP aerosol shall have a particle size distribution with count median diameter of 0.185 ±0.020 µm and a standard geometric deviation not exceeding 1.60 at the specified test conditions as determined with a scanning mobility particle sizer or equivalent.

(e) The test will continue until minimum efficiency is achieved or until an aerosol mass of at least 200 ±5 mg has contacted the filter. For PAPR100-P series filters, if the filter efficiency is decreasing when the 200 ±5 mg challenge point is reached, the test will be continued until there is no further decrease in efficiency.

(f) The efficiency of the filter will be monitored and recorded throughout the test period by a suitable forward-light scattering photometer or equivalent instrumentation.

(g) The minimum efficiency for each of the 20 filters will be determined and recorded and must be equal to or greater than the filter efficiency criterion for PAPR100-N and PAPR100-P, efficiency ≥99.97 percent, pursuant to §84.170(b).