Protectoseal Series No. 18540, Pipe-Away Pressure / Vacuum Conservation Vent, is designed to provide pressure and vacuum relief in applications that require hazardous vapors to be piped away, rather than released into the atmosphere. The pallets in the vent housing allow intake of air and escape of vapors as the tank normally breathes in and out. Pallets open and close to permit only that intake or outlet relief necessary to remain within permissible working pressures and avoid tank damage. Relieving vapors may be piped away through a flanged connection one size larger than inlet providing greater flow capabilities.