Abstract: A valve for controlling the pressure within a tank to prevent excessive above or below atmospheric pressure conditions, including a pressure responsive valve and a vacuum responsive valve, wherein each valve includes a pallet with seals and blowdown rings of polytetrafluorethylene material, which is commercially marketed under the trademark Teflon. The pressure pallet includes guide means having Teflon parts, while the vacuum responsive valve includes hinge means having coacting Teflon parts. The breather valve includes structure defining a vertically extending vent structure having an opening arranged alongside the tank in which the valve is mounted, which opening is positioned to avoid being sealed by any normal buildup of ice and snow.