the respirator is negative compared to the pressure outside the mask

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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.
The fit of the respirator depends on two important design features:
Is the working mode of the respirator "negative pressure" or "positive pressure"
Type and extent of facial coverage
Respirators operating in "negative pressure" mode require the wearer to draw air into the mask through an air purification device (filter or chemical cartridge) so that the pressure generated inside the respirator is negative compared to the pressure outside the mask. On the other hand, a "positive pressure" respirator pushes clean air into the mask through a fan or compressor, so that the air pressure inside the mask is greater than the air pressure outside the mask. Negative pressure respirators provide less protection than positive pressure respirators because the former is more prone to internal leakage.
The design of the face is also important-some designs are more suitable for the face than others. Half-mask respirators (covering only the mouth and nose) are more difficult to install than full-face respirators (also covering the eyes). The nose and chin are the most difficult facial features to establish a close connection. The fit of a hood, helmet or "loose" mask is highly dependent on the specific design and configuration. For detailed information about the different levels of respirators and their protection levels, please refer to the NIOSH respirator special page and OSHA respiratory protection standards
Because health is so important, NIOSH recommends that OSHA require each respirator wearer to undergo an initial health test and then perform a health test every year thereafter. It is impossible to predict how much a respirator can play on a particular face, even if the respirator can adapt well to different facial sizes. FDA does not recommend or require any tests suitable for surgical masks. The published research on the performance of surgical masks is very limited. Three clinical studies conducted in the 1980s and 1990s found that when workers did not wear masks, there was no difference in surgical infection rates. 1, 2, 3
A recent laboratory study of five masks with "good" filters found that 80-100% failed one using Bitrex OSHA-accepted qualitative compliance tests (bitter tasting aerosols) and quantitative factors ranging from 4-8 leaks 12-25%) Use TSI Portacount. 4 In contrast, at least the protective type of respirator (negative pressure half mask) must have a suitable factor (particle concentration divided by internal concentration) at least 100 leakage (1%) .
NIOSH would like to hear your experience using NIOSH approved respirator and fda approved surgical mask. For example, can NIOSH help solve the user's need for increased comfort and wear resistance? Do users feel that the exhalation valve on the disposable filter mask will affect the wearer's ability to successfully perform the user's seal inspection? Is the design of the filter mask mask Some aspects need improvement to better suit? How do you compare the comfort and wear resistance of medical masks and filter masks?
In addition, the NIOSH Respirator Trusted Source Information page can help users identify NIOSH approved respirator and learn how to use and obtain these products. " Wholesale Surgical Mask