Noling ventilation pipe cast iron artificial anti-ventilation smoke exhaust pipe high-strength high-temperature resistant The circular civil defense pipe produced by Texas Norling Ventilation Equipment is made of black iron, that is, carbon steel, and is used as a connecting device in civil defense projects. Generally, it is used a lot in civil defense projects. Civil defense projects are people's air defense. They refer to actions taken by mobilizing and organizing the masses to defend against enemy air attacks and eliminate the consequences of air strikes. It is referred to as civil defense for short. Foreign countries often combine wartime air defense implemented with the participation of the public with normal disaster relief, which is called civil defense. Civil defense ventilation ducts are pipes used to exhaust air in civil air defense projects. Civil defense pipelines play the role of ventilation and dehumidification in general basements, and ventilation, dehumidification and smoke exhaust in civil defense basements. Although the underground garage is uninhabited, there are people entering and exiting, so it is also necessary to have air quality suitable for human survival; there are very few natural vents in the basement (generally only entrances and exits), which is far from the required amount of ventilation; not to mention that basements are often humid (especially during the rainy season), and strong ventilation is necessary to reduce humidity. Some garages also have a man-made defense function. Considering that they are used for temporary residence under special circumstances (in general, during war, imports and exports are closed, a large number of people take refuge in them, and consider that smoke and other fireworks will pour into the basement during war), so ventilation and smoke exhaust must be considered.