KN95 Face Mask (10 pcs)

When the oxygen concentration is lower than 19.5% in anoxic environment, the mask is not suitable for use.The concentration of pollutants is too high to endanger life or health. It is not suitable to use this mask when the degree is high.The mask shall not be used to protect harmful gas or steam.When it is found that the mask is contaminated, damaged or the respiratory resistance changes.The mask should be replaced in case of major conditions.