According to general practitioners in the United States, it has been medically confirmed that small particles smaller than 2.5 microns (called PM2.5) can cause severe inflammation, which can lead to heart disease, lung disease and cancer. However, reducing exposure to polluted air can help improve people’s health, reduce the number of emergency room visits, and reduce overall deaths. Masks can help reduce contact with polluted air.

Construction sites all over the world are full of dust, heavy metals and dangerous gases. Test results from independent laboratories have proved that for decades, construction workers have relied on masks made by companies like 3M to greatly reduce their contact with polluted air, because these masks have a filtering efficiency of at least 95% for inhaled air.

This is exactly the meaning of "95" in the "N95 mask" we often see. (The N95 mask is one of the 9 anti-particulate masks certified by the National Institute of Occupational Safety and Health in the United States. Under the testing conditions specified in its standard, the filtration efficiency reaches 95%. N95 is not a specific product name. As long as it meets N95 Standards and products that pass the review can be called "N95 masks".)

In the N95 mask test, one person wears the mask for about 15 minutes. The person wearing the mask should move in many places. The mask is connected to a special machine to record the particle concentration inside and outside the mask. If the reduction of particles in the air inside the mask exceeds 95%, then the mask has passed the N95 test. Many masks have obtained this certificate. In view of this, it can be determined that these masks can greatly reduce our exposure to dangerous PM0.3-PM2.5 particles in air pollution.

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