為了(le)防止無(wu)(wu)塵(chen)室(shi)受(shou)到污染，室(shi)內(nei)必(bi)須保(bao)(bao)持(chi)(chi)正壓，如(ru)果無(wu)(wu)塵(chen)室(shi)內(nei)壓力過(guo)高，造(zao)成門(men)(men)扇不易開關，因而使(shi)用液(ye)壓閥(fa)門(men)(men)來保(bao)(bao)持(chi)(chi)無(wu)(wu)塵(chen)室(shi)內(nei)之(zhi)微正壓，通過(guo)泄壓風門(men)(men)的風量一(yi)般(ban)在(zai)100-120m3/h之(zhi)間，保(bao)(bao)持(chi)(chi)壓差(cha)在(zai)5-40Pa之(zhi)間。