Why can slow decompression be considered the most dangerous type of decompression?

Slow decompression is often considered the most dangerous type of decompression because it can occur subtly, leading to a situation where individuals may not immediately recognize the signs and symptoms of hypoxia, which is a deficiency of oxygen reaching the tissues. This gradual reduction in cabin pressure can allow the body to start experiencing hypoxia without a rapid change in environment, meaning that individuals may not experience the acute awareness or urgency that often accompanies sudden shifts in pressure.

Due to this undetectable onset, passengers could remain unaware of their deteriorating condition, which can result in impaired cognitive and physical abilities. Additionally, slow decompression increases the risk of developing decompression sickness (DCS), as the body does not expel nitrogen as efficiently under gradually decreasing pressure. The combination of these factors—unawareness of the situation, the potential for severe physiological effects, and the overlapping symptoms of hypoxia and DCS—renders slow decompression particularly hazardous compared to other types.

In contrast, other types of decompression, such as rapid cabin loss or sudden pressure differentials, typically produce more immediate reactions and awareness, prompting quicker responses to these emergencies.