Normally open type scavenging air valve

A normally-open type ventilation valve comprises a ventilation round pipe, the top end of the ventilation round pipe is provided with a breathing inner cover and a breathing outer cover in a covering mode, the breathing outer cover is arranged on the outer side of the breathing inner cover in a covering mode, a fixing plate is arranged at the top end of the ventilation round pipe, and the breathing inner cover and the breathing outer cover are fixed to the fixing plate through fixing bolts. A protective bottom outer cover is arranged on the ventilation round pipe and arranged between the inner breathing cover and the outer breathing cover. Compared with the prior art, the wine storage tank has the advantages that air is communicated with air in the tank through gaps among the breathing outer cover, the breathing inner cover and the protective bottom outer cover, so that negative pressure or positive pressure is prevented from being formed in the tank due to input and output of wine in the wine storage tank, a