Flying after pool diving FAQ

I’m a dive instructor, and I occasionally have student divers who wonder if they need to follow the flying-after-diving recommendations after just being in the pool.

Flying or travel to altitude after diving is a consideration for many divers, so it is great that the question is being asked. Fortunately, a typical shallow, low-workload, pool-diving exposure would be of minimal concern, particularly when the time is split between the bottom and the surface and the cumulative total underwater time is modest. This is a great opportunity, however, to reinforce an understanding of dive tables.
You can reference the U.S. Navy Diving Manual (USN 2008) for this guidance. An actual bottom time (the time from leaving the surface to the point of direct ascent to a stop depth or the surface) of 61-88 minutes at 15 feet of seawater (fsw) would put a diver in repetitive group C (Table 9-7). C is the maximum repetitive group allowed for immediate exposure to an altitude of 8,000 feet (Table 9-6). A maximum depth of 10 fsw would require an actual bottom time of 102-158 minutes to put a diver in repetitive group C.
Any delay between exiting the water and travel to altitude would provide an additional safety buffer as the diver offgases. Conversely, deeper dive depths, high underwater workloads and/or travel to higher altitudes would require greater conservatism.
Practically speaking, a 60-minute pool session in a 10- to 12-foot-deep pool would offer little concern for typical pressurized aircraft cabin altitudes (usually 6,000-8,000 feet altitude equivalent) or unpressurized flight or driving to a similar actual altitude. Following the flying-after-diving guidelines recommended for recreational diving would not be necessary for this (or lesser) exposure.
For completeness, the flying-after-diving guidelines for recreational diving call for a minimum 12-hour surface interval (SI) after single no-decompression dives, an 18-hour SI after multiple dives per day or multiple consecutive days of diving, and a “substantially longer” than 18-hour SI after decompression dives (Sheffield and Vann 2004). The “substantially longer” text was used to acknowledge the fact that we did not have sufficient data for precise recommendations, but it is a common rule of thumb that a 24-hour SI is desirable for decompression dives.
The DAN® flying-after-diving guidelines are applied to the altitude range of 2,000-8,000 feet. Exposures to altitudes below this range are ignored, and exposures to greater altitudes are not recommended after diving until all excess inert gas is eliminated. In comparison, the U.S. Navy uses 1,000 feet as the threshold for altitude exposure. An interesting fact is that the U.S. Navy tables rely on most of the same data used to generate the DAN guidelines. The specific guidance for different exposure profiles is primarily based on mathematical manipulation of the same data, not additional experimental data.
— Neal W. Pollock, Ph.D.
References
Sheffield P, Vann RD, eds. DAN Flying After Diving Workshop Proceedings. Durham, NC: Divers Alert Network, 2004.
U.S. Navy Diving Manual, Volume 2, Revision 6. NAVSEA 0910-LP-106-0957. Washington, DC: Naval Sea Systems Command, 2008: Chapter 9.