A.10mg/m3(15ppm) B.30mg/m3(20ppm) C.30mg/m3 D.15mg/m3(10ppm)
A.一級 B.二級 C.三級 D.四級
A.30mg/m3(20ppm) B.20mg/m3(30ppm) C.3mg/m3(2ppm) D.2mg/m3(3ppm)