Lim lub qhov ncauj qhov ntswg txwv los ntawm ib puag ncig

The use of filter-type respiratory protective equipment must be limited by the environment. When there are harmful substances in the environment that cannot be filtered by the filter material, or the oxygen content is less than 18%, or the concentration of toxic and hazardous substances is high (>1 feem pua), Hauv kev siv, cov cuab yeej tiv thaiv kab mob sib cais yuav tsum tau siv rau hauv ib puag ncig no.