According to the harmful gas density and the density of the air of different size, there are many ventilation cabinet form ventilation cabinet, local application of different forms of different. Contains the main form of ventilation cabinet: ventilation cabinet is exhaust ventilation cabinet, a lower air exhaust, ventilation cabinet wind combined discharge of up and down. At the same time, supply ventilation cabinet and energy saving.
Hood face velocity ventilation cabinet is main technical index to measure the performance of fume hood, it refers to the exhaust hood of the average wind speed at the entrance opening doors, ventilation cabinet hood face velocity selection criterion is: we should make harmful gas cannot escape from the cabinet, but also to avoid the turbulence in the ventilation cabinet.
High face velocity turbulence above the space station can work lead to exhaust air in the cabinet in the cabinet, pollutants may be in a corner to accumulate, and can blow out the flame, the test failure is ongoing, hood face velocity is too low will cause pollutants escape, hazard testing the safety of personnel.