Diving using mixed gas involves the use of breathing gases other than air or EANx to enable divers to explore greater depths. Mixed gases, such as helium and oxygen (HELIOX), helium, nitrogen, and oxygen (TRIMIX), are employed in both open circuit SCUBA and rebreather equipment. WorkCover Queensland emphasizes that using mixed gases requires meticulous planning, gas analysis, training, and proper equipment to ensure safe diving practices.

Rebreathers, which utilize a breathing circuit rather than an open system, maintain air quality through chemical absorption, removing carbon dioxide while adding oxygen and diluents. These systems employ in-line sensors and computers to monitor breathing gas, providing alerts to divers when necessary. While rebreathers offer benefits like quietness and efficient gas usage, risks include system flooding and failures in the breathing circuit components, potentially leading to toxic or hypoxic breathing gas.

In the context of SCUBA diving with mixed gas, WorkCover Queensland outlines the responsibilities of the person conducting the business or undertaking. This includes ensuring the presence of a dive supervisor at the dive site and limiting recreational mixed gas scuba diving to certificated individuals. Guidelines emphasize avoiding exceeding oxygen and nitrogen partial pressure exposure times, as well as specific depth limits. Gas analysis before use and comprehensive advice to divers, covering dive plans, gas changeover depths, emergency procedures, and equipment checks, are critical safety measures.

For mixed gas rebreather diving, WorkCover Queensland underscores similar responsibilities for the person conducting the business or undertaking. This includes the presence of a dive supervisor, certification requirements, and adherence to oxygen partial pressure exposure limits. Additionally, guidelines address maximum dive depth, gas analysis, and precautions against using rebreathers for non-certificated diving experiences. Divers are advised on dive plans, omitted decompression procedures, equipment checks, safety requirements, and emergency procedures, reinforcing the importance of adhering to manufacturer guidelines for pre-dive checks and handling carbon dioxide scrubbers.