In today's world, there are primarily two major standards for protective masks: the American standard and the European standard. China has recently introduced its own new standard for masks, which is largely based on the American model.
The American Standard, known as the NIOSH (National Institute for Occupational Safety and Health) standard, categorizes masks into three types: N, R, and P. These categories represent different levels of protection against various types of particles. N-type masks are designed for non-oily particles, while R and P types are used for oily particles. However, R-type masks are only effective for up to 8 hours, whereas P-type masks have no such time restriction. Each category has three levels of filtration efficiency: 95 (95%), 99 (99%), and 100 (99.97%). This results in a total of nine mask standards. Since biological particles are typically non-oily, the N95 mask is considered the most basic and widely used, offering 95% filtration efficiency for non-oily particles at a flow rate of 85 L/min.
The European Standard, CE EN 149:2001, divides masks into three levels: FFP1, FFP2, and FFP3. Unlike the American standard, the European test uses a higher flow rate of 95 L/min and tests with DOP oil, which simulates oily particles.
China’s standard, GB19083-2003, follows the American model but only includes the N95 level. It uses sodium chloride (NaCl) particles, which are non-oily, with a flow rate of 85 L/min. The average particle size is 0.26 μm, and the counted particle size is 0.07 μm. When the filtration efficiency reaches 95%, the airflow resistance must not exceed 35 mm water column.
Some masks are labeled with BFE (Bacterial Filtration Efficiency) ≥ 95%. This test, developed by the Nelson Laboratory in the U.S., uses 3.0-micron particles at a flow rate of 32 LPM to measure the material's ability to filter bacteria.
Regardless of whether the standard is American or European, testing is usually conducted using the TSI-8130 Automated Filter Tester. For N-type masks in the U.S., the NaCl method is used, while R-type masks use the DOP method. In Europe, the DOP method is also employed.
The TSI-8130 instrument uses the NaCl method to generate salt particles, with an average diameter of 0.2 μm (aggregate average of 0.26 μm, arithmetic average of 0.07 μm). It automatically measures flow rate, resistance, and transmittance through the sample. The DOP method, on the other hand, generates oil particles with an aggregate average diameter of 0.33 μm and a counted average of 0.20 μm.
These standards help ensure that masks provide adequate protection against a wide range of airborne particles, making them essential in both industrial and public health settings.
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