BIRNS Model 4132 General Area Chamber Light-- Frequently Asked Questions At what pressure is the relief valve set to relieve the pressure? Are other lens colors available? At what pressure is the relief valve set to relieve the pressure? Is that tested prior to shipment? This valve is set to "crack" (i.e. relieve pressure) at a pressure differential of 5 PSI. Our standard production test does not include confirming the cracking pressure prior to shipment, although we do perform a manual operational test as standard. Are other lens (dome) colors available? Yes! Although the standard lens (dome) is clear, we can also supply amber or red domes on special order. Top