Flying and Scuba Diving: Safety Guidelines
Diving and flying are two activities that often overlap, and although nearly all open water courses point up the risks of going to altitude after scuba, divers still have quite a few questions about specific recommendations on the topic. What are the safe intervals between flying and scuba diving? Why is it necessary to wait? Do the same rules apply to driving or hiking to high altitudes? We’ll answer these and a few other questions in the article below.
Why is it dangerous to fly after scuba diving?
The main concern with scuba diving and flying is decompression sickness. As you must know from your scuba certification course, your body needs to have adequate time during an ascent to off-gas excess nitrogen or you can form bubbles in your bloodstream, possibly leading to DCS.
If you fly directly after diving, the decreased ambient pressure in the plane has the same effect as ascending too quickly from a dive. It can cause residual nitrogen in your blood to come out of solution too rapidly, creating large nitrogen bubbles in your blood stream. Staying at ground level before going to altitude is essentially like doing a decompression stop.
Aren’t airplane cabins pressurized?
On a typical commercial jet, the cabin is pressurized to the equivalent of approximately 8,000 feet, which is still a pressure decrease from sea level of 25 percent. If your body is already off-gassing at sea level as fast as it can, this sudden decrease in pressure could be enough to trigger symptoms of DCS.
What about flying in small planes?
Flying in a small personal or chartered plane may require even more caution since many such aircraft do not have pressurized cabins and will regularly fly higher than 8,000 feet. In non-commercial aircraft, a pilot may easily hit 10,000 - 16,000 feet in an unpressurized cabin without any oxygen requirements becoming effective. This added altitude and lesser atmospheric pressure could enhance decompression-related effects.
How long should I wait before flying?
Unfortunately, there is no straightforward answer to this question. The number of dives undertaken during the trip, the type and pattern of dives completed (decompression, non-decompression, altitude dives, nitrox, etc.), your general health, body type, and your age, as well as the maximum altitude you will be flying at should all be considered before making a decision.
Even when it comes to general recommendations on safe intervals before flying, different organizations have different takes on the subject. Both PADI and DAN recommend a minimum preflight surface interval of at least 12 hours for single dives and 18 hours for repetitive dives or multiple days of diving. The US Air Force recommends 24 hours after any dive, while the US Navy tables recommend only 2 hours before flying to altitude. There’s also the FAA’s Airman’s Information Manual (AIM), which offers a small section entitled “Decompression Sickness After Scuba Diving” and indicates that a diver should wait at least 12 hours prior to flying to altitudes up to 8,000 feet (MSL) if a dive has not required a “controlled ascent” (no-decompression diving) and at least 24 hours after diving in which a “controlled ascent” is required. Any flight above 8,000 feet Mean Sea Level should be delayed until at least 24 hours have elapsed.
|Organization||Recommended Surface Interval Before Flying|
|DAN||12 hours (for single no-decompression dives)
18 hours (for multiple no-decompression dives)
|PADI||12 hours (for single dives)
18 hours (for multiple dives)
|US Air Force||24 hours|
|US Navy||2 hours|
|Federal Aviation Administration||12 hours (for no-decompression dives and altitudes below 8,000 feet)
24 hours (for dives requiring decompression stops or altitudes over 8,000 feet)
So what is the best course of action?
Research shows that the estimated probability for developing DCS when flying with a 12 hours surface interval is around 1 percent. Of the divers who fly home between 12 to 24 hours after their last dive, only an estimated 0.004 percent will develop symptoms of DCS. Therefore, having a “down day” (full 24 hours) prior to flight after any diving is considered good practice. Two days might be an even better plan, especially you did at some point any deep, repetitive or decompression diving.
It’s completely understandable that we all want to make the most of your scuba diving holidays and often try to squeeze in as many dives as possible, however, it isn’t worth putting your life at risk. Just plan a day off and take it as an opportunity to explore some other cool activities and places around. Go sightseeing, wildlife viewing or even snorkeling.
Can I use a dive computer to tell me when it’s safe to fly?
Many modern dive computers have a “time-to-fly” feature, which basically shows a recommended wait time for a diver prior to a flight. However, different computers have two different ways of dealing with the issue:
- Arbitrary countdowns. These are simply clocks reminding you of the twelve or twenty-four-hour rules; they perform no calculations.
- Calculation to desaturation. These computers (normally using their no-decompression algorithm) will calculate the time to total desaturation (or before our bodies have off-gassed enough for ambient pressure to be reduced to more than 6,000-8,000 feet of altitude) and use that as the time to fly. Although more realistic, this method is not very practical in terms of planning. Because many manufacturers use different decompression algorithms and every dive profile is different, it is difficult to estimate what that no-fly time will be in order to plan a return flight home.
If you do use a dive computer to calculate your no-fly times, remember that you must use the same computer on every dive for the calculations to be accurate, as they are cumulative based on diving times, depths, and the number of dives.
What about driving or hiking to high altitudes?
Since the problem with flying is basically the decrease in ambient pressure, driving or hiking to higher altitude will have the same risk. This is especially important to remember since, in many popular diving destinations, such as Bali, Canary Islands, Hawaii or South Sinai in Egypt, a lot of attractions and activities take place up in the mountains. So, if you know that on your way home you have to drive through a mountainous area, or you want to go hiking to an area that causes you to experience a change in altitude, be sure to wait enough time after scuba diving.
Is diving after flying safe?
Diving after flying does not in itself create a decompression problem, so there are no set guidelines for when to make your first dive. However, simple fitness to dive can be an issue. Long-distance air travel is tiring, dehydrating and often generally stressful. Fatigue and disorganization, in turn, can affect your performance and safety during the dive. So it is best that you build some pre-dive flight recovery time into your travel plans to make sure you are well rested and ready.