Automatically senses change in air flow and shuts off the flow in the event of a surge in excess of valve rating. Fully conforms to OSHA regulation 1926.302 requiring safety device at source of air supply and at branch air lines. Controls air flow in only one direction, however, permits flow in either direction. The cut off flow of the selected valve must be less than the actual flow that would occur should a hose or coupling fail. The valve selection must be based on additional guidelines other than compressor rating or hose size. Air flow (scfm) varies with distance of flow and restrictions within each system. Select the pipe size which is the same as the hose with which it will be used. To avoid nuisance cutoffs, the valve should have a nominal cut off rating of 110% of the maximum consumption of the air tool to be used. Install a cut off valve in each line and branch line subject to rupturing or accidental disconnection. Test each valve for proper function at installation and periodically thereafter. The only time one of these valves will not perform properly is when the tool usage and maximum line flow are close to equal. When start-up is underway, open the Air Control Valve at the Compressor or Manifold VERY SLOWLY to allow air to bleed through the Check Valve so that pressure is equalized on each side of the valve. If the valve fails to operate despite meeting all conditions, check the hose line for obstructions or a Hose Mender restricting normal air flow. Maximum Working Pressure: 250 PSI. Brass construction.