"How are surgical masks and respirator filters detected?" The website: https://www.maskwholesales.com
The respirator filter must comply with the strict certification test (42 CFR Part 84) established by NIOSH. The NIOSH test uses parameters that are considered "worst-case", including:
Sodium chloride (series filter) or dioctyl phthalate oil (R-p series filter) test aerosol particle mass average aerodynamic diameter is about 0.3µm MPPS-range for most filters
The air flow rate is 85 L / min, which is a medium to high working rate
Before testing, adjust for 24 hours at 85% relative humidity and 38 ° C
Initial breathing resistance (resistance to airflow) does not exceed 35mm water column * height pressure and initial expiratory resistance does not exceed 25mm water column height pressure
A charge-neutralized aerosol
The minimum amount of spray is 200 mg, which means that the exposure in the workplace is very high
During the NIOSH certification test, the filtration efficiency cannot be lower than the certification level
* The millimeter of the water column is the unit to measure the slight pressure difference. It is defined as the pressure exerted by a 1 mm high water column under specified conditions, such as 39 ° F (4 ° C) under standard gravity.
Due to these strict performance parameters, the fiber diameter, porosity and filter thickness of all particulate filters used in niosh certified respiratory protective masks (including N95s) are designed and designed to provide very high particulate collection efficiency in MPPS .
On the other hand, manufacturers of surgical masks must prove that their products are at least as good as the masks already on the market in order to obtain marketing "licenses." Manufacturers may choose to use biofilters to test the flow of bioaerosols at 28 L / min (bacterial filtration efficiency) or 0.1 aerosol µm latex balls and a speed range from 0.5 to 25 cm / sec (particulate filtration efficiency). It should be noted that the US Food and Drug Administration stipulates that latex ball aerosols cannot be neutralized by electric charges.
Testing the production of aerosols can cause the percentage of aerosolized particles to be higher than the percentage normally expected in workplace exposure. The charge neutralization test aerosol, like the aerosol used in the NIOSH test, reduces the charge on the aerosol particles to an equilibrium state. Therefore, compared with the use of charge-neutralizing aerosols, due to the electrostatic attraction of the filter to collect charged particles, a higher filtration efficiency value may be produced. In addition, allowing manufacturers to choose a range of air flow rates means that the test results can be easily manipulated. In general, particles are collected with higher efficiency through a filter at a lower speed.
The tests produced by these two aspects are not necessarily "worst-case" surgical mask filters. Because the performance parameters of medical masks are not as strict as the filters used in niosh certified respirators, the design of the fiber diameter, porosity and filter thickness of medical masks greatly reduces the particle collection efficiency.
How do surgical masks and respirator filters work?
Respirator filters that collect at least 95% of the aerosol get 95 points. Those who get at least 99% will get "99" points. Schools that scored at least 99.97% (essentially 100%) scored 100 points. The degree of protection of the respirator filter is N, R or P. This rating is very important in industry, because some industrial oils can remove the static charge in the filter medium, thereby reducing (decreasing) the filtration efficiency performance. If the gas mask is not resistant to oil, it is rated "N"; if it has a certain resistance to oil, it is rated "R"; if it has strong resistance to oil, it is rated "P" (oil resistant) . Therefore, there are 9 types of particulate mask filters:
N95 N-99 N-100
R-95, R-99, and R-100
P-95, P-99 and P-100 "