The Fig. 749 Vent valve is used on underground & low volume aboveground tanks for motor fueling. The vent allows the tank to "breathe" during filling/ dispensing operations. Poppets seal vapors in the tank when pressure is equalized. Settings are approximate. Fig. 749CRB0500 and 749CRBS500 offer C.A.R.B. approval for Stage I vapor recovery systems. Fig. 749CRB0600 and 749CRBS600 offer C.A.R.B. approval for Stage I & II vapor recovery systems.