How many psi does the reserve hold back in a double cylinder configuration?

In a double cylinder configuration, the reserve typically holds back 250 psi. This practice ensures that a diver has a minimum amount of gas reserve to safely ascend to the surface in case of an emergency or if the primary supply is depleted. Maintaining this reserve is crucial for safety during dives, as it provides a margin of safety to accommodate for any unforeseen circumstances that might arise underwater. This 250 psi of reserve gas acts as a safety buffer, enabling divers to manage their ascent properly and perform necessary safety stops, which are vital for preventing decompression sickness.

Understanding the importance of this reserve helps divers make more informed decisions during their dives, ensuring their safety and that of their diving partners.