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 "
"Respirator filters are regularly tested by NIOSH during and after use to ensure that they continue to meet certification testing standards." The FDA has not independently evaluated the filtering performance of surgical masks and has not published the manufacturer's test results. In many cases, it is difficult to find information about the filtering test results of fda removal surgical masks. The surgical masks removed by the US Food and Drug Administration (fda), known as surgical N95 masks, are a notable exception to the uncertainty of filtration performance. This is the only surgical mask that includes strict NIOSH standard evaluation. All members of this type of masks have been approved by NIOSH as N95 masks before obtaining FDA approval. The FDA partially acknowledges that the NIOSH filtration efficiency and respiratory resistance test results exceed the requirements of ordinary surgical masks.
In studies comparing the performance of surgical mask filters using standardized airflow, the filter performance proved to be highly variable. When measured using NIOSH certified test parameters, the collection efficiency of mask filters from masks of different manufacturers can vary from less than 10% to close to 90%. The test results required by fda (if any) do not predict their performance in these studies.
It is important to remember that the overall performance of any surface filter depends on, first of all, good filter performance. A face mask or face mask that does not provide a high level of protection if the filter is not good.
Respirator and surgical mask are suitable
Because respirator filters must meet strict certification requirements, the collection efficiency of various aerosols encountered in the workplace is always very high. Recently, there have been concerns that the respirator filter will not collect nanoparticles, but studies have shown that the efficiency of collecting these particles meets NIOSH standards. This is not surprising because the NIOSH test uses small, charge-neutralized, relatively monodispersed aerosol particles and high airflow.
Therefore, the most important aspect of the performance of the respirator certified by niosh is its degree of fit with the face and the degree of leakage around the mask to a minimum. This must be measured for everyone and the respirator they choose. Choosing the right protective mask for a specific workplace depends largely on choosing the right level of protection. Wholesale Protective Suit
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