What is Active Addition for Semi-Closed Circuit Rebreathers?
The active addition system is a key component of SCRs, controlling the feed gas’s addition to the breathing loop. The mechanism adds a specific quantity of gas regardless of the current loop volume, providing a constant supply of breathable gas while preventing hyperoxic or hypoxic conditions. At its core, the active addition system consists of a supply valve controlled by the diver or an electronic mechanism. When the diver inhales, the decrease in loop volume triggers the valve to release more gas into the loop. In electronically controlled systems, gas is added at fixed intervals, ensuring a continuous supply.
What is Surface Consumption Rate?
The Surface Consumption Rate (SCR) is a critical concept in scuba diving that quantifies a diver’s gas usage under standardized surface conditions. This value is measured in units such as pounds per square inch (psi), bars, or cubic feet per minute (CFM). SCR is an essential metric for calculating a diver’s air consumption at different depths and plays a significant role in dive planning. Having an accurate understanding of one’s SCR is key for determining the duration of a dive, ensuring a safe and well-managed air supply throughout the dive.