What is the primary purpose of documenting fill logs in diving?

The primary purpose of documenting fill logs in diving is to ensure safe gas mixes. Fill logs serve as a record of the specific gas mixtures that divers receive in their tanks, including the percentage of oxygen and nitrogen. Proper documentation is crucial because it helps divers and dive operations verify that the gas they are using is safe for their planned dives, especially when using enriched air nitrox, which has elevated oxygen levels. Knowing the exact contents of the tanks allows divers to calculate their exposure to oxygen and adjust their dive plans accordingly to avoid oxygen toxicity.

The accuracy of fill logs also supports proper planning for dive profiles, ensuring that the diver can safely manage their ascent, decompression stops, and overall dive duration. Inaccuracies in the gas mix can have serious safety implications, making tracking and documentation vital for diver safety.