Why should oxygen readings be taken prior to the dive?

Taking oxygen readings prior to the dive is crucial to ensure safe levels of oxygen in the mixture. Excessive oxygen concentrations can lead to oxygen toxicity, especially at deeper depths, where partial pressures increase. By measuring the oxygen percentage in the nitrox blend, divers can confirm that the mixture meets safety standards for their planned dive profile. This verification helps in planning the dive safely, managing the risks associated with elevated oxygen levels, and ensuring that divers have a clear understanding of the gas they will be breathing while underwater.

Other aspects such as weather conditions, temperature variations, and dive duration are important considerations for diving, but they do not directly relate to the safety of the gas mixture that divers will be using. Focusing on oxygen levels specifically addresses the critical need for safe breathing gas mixtures at depth.