嚴格控制通風(feng)柜(ju)的風(feng)量風(feng)速(su)是(shi)因為有害氣體密度與空(kong)氣密度大小都是(shi)不(bu)同的，所以(yi)對通風(feng)柜(ju)罩面(mian)風(feng)速(su)要求(qiu)就會有所不(bu)同。

　　通(tong)(tong)風(feng)(feng)(feng)(feng)(feng)柜(ju)可以(yi)分為上(shang)部(bu)排風(feng)(feng)(feng)(feng)(feng)的通(tong)(tong)風(feng)(feng)(feng)(feng)(feng)柜(ju)，下部(bu)排風(feng)(feng)(feng)(feng)(feng)的通(tong)(tong)風(feng)(feng)(feng)(feng)(feng)柜(ju)和上(shang)下聯合排風(feng)(feng)(feng)(feng)(feng)的通(tong)(tong)風(feng)(feng)(feng)(feng)(feng)柜(ju)，還(huan)有節(jie)能型的供(gong)氣式通(tong)(tong)風(feng)(feng)(feng)(feng)(feng)柜(ju)。通(tong)(tong)風(feng)(feng)(feng)(feng)(feng)柜(ju)罩(zhao)面風(feng)(feng)(feng)(feng)(feng)速(su)(su)就是指(zhi)排風(feng)(feng)(feng)(feng)(feng)柜(ju)開口(kou)拉門(men)處的平均入口(kou)風(feng)(feng)(feng)(feng)(feng)速(su)(su)。對通(tong)(tong)風(feng)(feng)(feng)(feng)(feng)柜(ju)要(yao)求的通(tong)(tong)風(feng)(feng)(feng)(feng)(feng)柜(ju)罩(zhao)面風(feng)(feng)(feng)(feng)(feng)速(su)(su)的準則(ze)是：有害氣體(ti)(ti)不能從柜(ju)內(nei)逸(yi)出，同時也要(yao)保證避免有害氣體(ti)(ti)在通(tong)(tong)風(feng)(feng)(feng)(feng)(feng)柜(ju)內(nei)產(chan)生紊流。

　　因(yin)此對(dui)通風(feng)柜(ju)的(de)(de)風(feng)量(liang)風(feng)速要(yao)嚴格的(de)(de)控制從而確保(bao)安全(quan)。因(yin)為過高的(de)(de)罩(zhao)面風(feng)速可能(neng)會(hui)使得排(pai)風(feng)柜(ju)內(nei)工作臺上方空間內(nei)氣流發生紊(wen)亂，污染物(wu)(wu)可能(neng)在(zai)柜(ju)內(nei)某個角落(luo)積聚，并(bing)且有可能(neng)吹熄火焰，破(po)壞正在(zai)進行的(de)(de)試驗(yan);而過低的(de)(de)罩(zhao)面風(feng)速會(hui)造成(cheng)污染物(wu)(wu)的(de)(de)逃逸，危害試驗(yan)人(ren)員的(de)(de)安全(quan)。