为防止管道施工堵塞,我单位试制成铸铁透气罩。透气罩的构造见图1。这两种透气罩的上部均不带孔,气由侧孔通过。因此,脏物不容易掉进。这种透气罩与透气立管同时安装,避免管口上部敞开,防止屋面施工中的砂石等杂物落入管内。铁制透气罩比较坚固,不易损坏。采用透气罩还可避免污水立 In order to prevent the construction of the pipeline from being blocked, our unit has trial-produced a cast iron ventilation hood. The structure of the air hood is shown in Figure 1. The upper part of the two kinds of breathable hoods are not provided with holes, and gas passes through the side holes. Therefore, dirt is not easy to fall into. This air-permeable hood is installed at the same time with the breathable riser, avoiding the open upper part of the nozzle to prevent sand and other debris from falling into the pipe during roof construction. The iron breathable cover is strong and hard to damage. Using a breathable hood can also avoid the sewage