It is important to know the blend’s maximum depth because:

Understanding the blend's maximum depth is crucial primarily because it helps prevent oxygen toxicity. When diving with enriched air, especially with higher levels of oxygen than normal air, divers are at risk of experiencing oxygen toxicity if they exceed the maximum depth for that blend. Each mix of enriched air has a specific maximum operating depth (MOD), determined by the percentage of oxygen and the partial pressures that can safely be tolerated. Diving deeper than this limit increases the partial pressure of oxygen in the mix, which can lead to adverse effects on the central nervous system and potentially life-threatening conditions.

This knowledge is essential for ensuring safety during the dive. While the blend's maximum depth also contributes to planning and could correlate to equipment setup in certain contexts, the primary importance lies in its role in preventing the physiological dangers associated with increased oxygen levels at greater depths.