42 C.F.R. § 84.172
Airflow resistance test
(a) Resistance to airflow will be measured in the tight-fitting respiratory inlet covering of a complete particulate respirator mounted on a test fixture with air flowing at continuous rate of 85 ±2 liters per minute, before each test conducted in accordance with § 84.173.
(b) Resistance of a complete tight-fitting powered air-purifying particulate respirator system will be measured with the blower off if the manufacturer indicates that the respirator should not be doffed in the event of a blower failure.
(c) The maximum allowable resistance requirements for air-purifying particulate respirators are as follows:
| Respirator type | Inhalation | Exhalation | |
|---|---|---|---|
| Initial | Final | ||
| Non-Powered (N, R, and P) | 35 | N/A | 25 |
| Powered (tight fitting) (HE class and PAPR100 class) | 50 | 70 | 20 |