A non-sterile device used to regulate the maximum pressure level in a circuit or system (typically containing gas) where it is essential not to exceed a pre-set maximum pressure. Should this pressure level be exceeded, this device will automatically open and vent the excess pressure from the circuit/system ensuring that an excessive pressure level is not sustained, thereby preventing damage to the patient or a parent device. It is typically used in anaesthesia machines and ventilators forming part of the breathing/gas delivery circuit/system, but may be applied to other functions. This is a reusable device.