How long to wait before flying after diving

The short answer

DAN's flying-after-diving guidelines, from a workshop it sponsored in 2002, recommend a minimum surface interval of 12 hours after a single no-decompression dive, and a minimum of 18 hours after multi-day repetitive diving. DAN Europe gives the same 12-hour figure.^2,4

For dives with compulsory decompression stops, or dives on heliox or trimix, the DAN guidelines do not give a fixed figure and recommend waiting substantially longer than 18 hours. A more recent Ask DAN column gives a figure of at least 24 hours after dives with mandatory decompression stops.^2,3

PADI's general advice is simpler: wait 24 hours before flying after any type of diving. These figures are minimums, and DAN notes that waiting longer than recommended further reduces the risk of DCS.^1,5

• Single no-decompression dive: at least 12 hours (DAN).²
• Multi-day repetitive diving: at least 18 hours (DAN).²
• Decompression dives: substantially longer than 18 hours (DAN guidelines); at least 24 hours (Ask DAN).^2,3
• Any diving, as a general rule: 24 hours (PADI).⁵

Why the wait matters

Under pressure at depth, inert gases such as nitrogen build up in the body's tissues. On ascent the process reverses and the gas leaves the tissues, but if elimination becomes disorderly, gas bubbles can form, which is what causes DCS.⁶

Going up to altitude lowers the surrounding pressure again, so DAN states that it increases the risk of DCS, and that the higher the altitude, the greater the risk. Airliner cabins are not kept at sea-level pressure: DAN gives an effective cabin altitude of generally 6,000 to 8,000 feet, with a maximum of 8,000 feet, or about 0.75 atmospheres absolute.¹

What the guidelines cover, and their limits

DAN says the guidelines apply to air dives followed by flights at cabin altitudes of 2,000 to 8,000 feet. They were based on chamber trials with dry, resting volunteers, and the workshop noted that longer intervals might be needed for divers who were immersed and exercising.^1,2

Dive computers can show a no-fly time. PADI advises waiting longer than the general guidance if the no-fly time on your dive computer says so.⁵

Driving over mountains and other altitude

The same reasoning applies on the ground. In an Ask DAN column, DAN says its minimum surface intervals apply to travel to elevations of 2,000 to 8,000 feet, whether by driving, hiking or flying. It points out that a car can climb over only one to two hours, which is not enough time for a recently dived body to adjust, and advises caution when planning the route home after a day of diving.³

PADI makes the same point: driving or hiking to the top of a 10,000-foot (3,048-metre) mountain carries the same risk as flying. It advises against mountain climbing in the first 24 hours after a dive, and says that if the journey home involves driving to altitude, you should allow a sufficient surface interval.⁵

If you have symptoms

DAN advises divers who notice signs or symptoms that may indicate DCS to seek medical advice and not to fly. The DAN workshop said divers need to be taught to seek medical advice rather than to fly if they notice such signs. For your own situation, talk to a dive physician or contact DAN.^1,2

Before you go

• Plan your last dive so you have at least 12 hours (one dive) or 18 hours (repetitive diving) before your flight, per DAN.²
• Allow more time after decompression dives: at least 24 hours according to Ask DAN.^2,3
• Check your dive computer's no-fly time; PADI advises following it if it is longer.⁵
• Check whether your road home climbs over a pass or high ground.³
• DAN notes that waiting longer than the minimum further reduces DCS risk.¹
• DAN advises seeking medical advice instead of flying if you notice symptoms that may indicate DCS.¹