If flying or ascending to altitude after diving, wait ____ hours after a single dive and _____ hours after a series of repetitive dives.

The correct response to the question about the waiting times for flying or ascending to altitude after diving is that you should wait 12 hours after a single dive and 18 hours after a series of repetitive dives. This guidance is grounded in the understanding of how nitrogen absorption and elimination in the body works.

After a dive, nitrogen is absorbed by the body tissues due to increased pressure underwater. Upon ascent and returning to the surface, this nitrogen must be safely eliminated to prevent decompression sickness (DCS). The recommended waiting times are designed to allow sufficient time for nitrogen levels to decrease back to safe limits.

For a single dive, 12 hours is suggested as this period typically allows for the majority, if not all, of the nitrogen from that single dive to adequately dissolve out of the body. Following a series of repetitive dives, nitrogen levels in the body are higher due to multiple exposures to elevated pressure over a condensed period, hence the longer wait of 18 hours to ensure a safer ascent to altitude or flight.

Following these recommended times minimizes the risk of DCS and enhances diver safety as they transition back to surface activities or travel.