Taco 400-4 1/8-Inch-NPT Float Air Hy-Vent Sturdy Brass Construction Maximum Pressure 150 psi Maximum Temperature 240F Designed for use on hot water radiators, baseboards, convectors, radiant panels, and small unit heaters with a maximum working pressure of 150 psi The Taco 400 HY-Vent can be opened (top is threaded on) and cleaned.