NFPA-99, requires that the Medical Gas Installer be notified when the contents of the Nitrogen Purge is running low. We have searched the industry and have found a replacement high pressure gauge that does just that. All you do is remove the high pressure gauge from your existing purging rig and replace it with the LO-N2 Alert Alarm Gauge. The battery is only being used when the unit is in alarm or while the test button is depressed. The unit has both a visual and audible alarm when the Nitrogen pressure falls below 500 psi +/- 150 psi. Bottom connection is ¼” NPT. An adapters to ⅛” is available.