Why do some valves have PE marked threads on their ports?-PFA valve, medication valve, explosion-proof valve, comprehensive manufacturer

Why do some valves have PE marked threads on their ports?: The PE port is a port for discharging the air pressure used by the internal pilot type. When switching, a small amount of air will be temporarily expelled. If the opening is blocked, it will cause poor operation, so please do not block it. If you mind the noise, please install a muffler. (Even if the exhaust of pilot valves such as NewSY adopts centralized exhaust, they may still have PE ports)