It may have been because the DVD burner was blocking the air vent.
它可能是因为DVD刻录机挡住了气孔。
2
Mechanical structure parts, vent-pipe of engine, combustion engine of boiler, burner.
机械构造用件，发动机排气管，锅炉燃烧室，燃烧器。
3
Before feeding water, air vent valves, pressure gauge valve, water level gauge, burner supply valve and steam supply valve should be opened fully. Other valves and checking manhole close.