NIOSH established the new test criteria to simulate worst-case respirator use and very severe test conditions. These filters can be used without particle size analysis or filter penetration testing in the workplace. R- or P-series filters should be selected if there are oil (e.g., lubricants, cutting fluids, glycerine) or non-oil aerosols in the workplace. N-series filters should be used only for non-oil (i.e., solid and water-based) aerosols.
| Note: To help you remember the filter series, use the following guide: N for Not resistant to oil |
The filter certification test is called worst-case (i.e., it produces maximum filter penetration) because the test conditions are the most severe that are likely to be encountered in a work environment. These conditions are:
- Air flow that simulates a high work rate (85 ± 4 liters per minute for single filters, 42.5 ± 2 liters per minute through each filter for paired filters)
- The most penetrating aerosol size (approximately 03 micrometer)
- Charge-neutralized particles
- The most filter-degrading test aerosol for R- and P-series filters
- Measurement of instantaneous (not average) penetration
- High total filter loading (up to 200 mg for N- and R-series filters, and continued loading until there is no further decrease in efficiency for P filters)
The degradation categories (N-, R-, and P-series) will be determined by using either sodium chloride (NaCB or dioctyl phthalate (DOP) as the test aerosol. NaCl is only slightly degrading to filter efficiency, whereas DOP is very degrading. Respirators tested with NaCl (i.e., N-series filters) are not resistant to efficiency degradation by oils and
