What should the first stage regulator be adjusted to if the EGS is left topside?

When the Emergency Gas Supply (EGS) is left topside, the first stage regulator should typically be adjusted to 150 PSIG. This pressure setting is crucial because it allows for a sufficient reserve of gas for emergency situations while also ensuring that the system operates optimally without over-pressurizing the equipment.

Setting it to 150 PSIG balances the need for adequate breathing gas supply for emergencies and maintains safety standards for the diver's equipment. Higher settings might lead to unnecessary complications and risks, such as equipment failure or increased stress on the diving system, while lower settings could compromise the availability of breathable gas during an emergency scenario. Therefore, the 150 PSIG setting is a reliable practice for ensuring both diver safety and equipment integrity when the EGS is being managed topside.