Preventing decompression sickness (DCS) comes down to controlling how fast dissolved nitrogen leaves your tissues as pressure drops. Every strategy, from ascending slowly to staying hydrated, works toward the same goal: giving your body enough time to release nitrogen gradually through your lungs rather than letting it form bubbles in your blood and tissues.
Why Bubbles Form in the First Place
When you dive, the increased water pressure pushes nitrogen from your breathing gas into your body’s tissues. The deeper you go and the longer you stay, the more nitrogen dissolves. This is perfectly fine while you’re at depth. The problem starts when you head back to the surface. As pressure drops, that dissolved nitrogen wants to become gas again. If you ascend slowly, nitrogen travels through your bloodstream to your lungs and gets exhaled. If you ascend too fast, nitrogen comes out of solution faster than your body can clear it, forming bubbles in your tissues and circulation. Those bubbles cause the joint pain, numbness, dizziness, and other symptoms of DCS.
Control Your Ascent Rate
The single most important thing you can do is ascend slowly. The U.S. Navy and NOAA recommend a maximum ascent rate of 30 feet (9 meters) per minute. Some recreational training agencies allow up to 60 feet per minute, but slower is safer. A good mental reference: don’t rise faster than your smallest exhaled bubbles. Most dive computers will warn you if you’re ascending too quickly, so keep yours visible and respond immediately to any alert.
Make Safety Stops Standard Practice
On any dive below 33 feet (10 meters), treat a safety stop as mandatory rather than optional. The standard protocol is to pause at 15 to 20 feet (5 to 6 meters) for three to five minutes before completing your ascent to the surface. This pause gives your body extra time to off-gas nitrogen from tissues that are still saturated. It’s a small time investment that meaningfully reduces bubble formation.
Plan Repetitive Dives Carefully
After surfacing from a dive, residual nitrogen continues to leave your tissues for hours. If you dive again before enough of that nitrogen has cleared, you start your next dive with a higher baseline of dissolved gas, which increases your DCS risk. Use your dive computer’s or dive table’s surface interval recommendations and don’t cut them short. For multiple dives in a day, do your deepest dive first and make each subsequent dive shallower. Allow adequate surface time between dives, and keep in mind that multi-day diving creates a cumulative nitrogen load.
If you’re flying after diving, the reduced cabin pressure at altitude creates the same conditions as a too-fast ascent. After a single no-decompression dive, wait at least 12 hours before flying. After multiple days of repetitive diving, wait a minimum of 18 hours. Longer intervals reduce risk further. Dives involving decompression stops or mixed gases like heliox or trimix call for substantially longer waits.
Use Your Dive Computer Wisely
Modern dive computers use algorithms that model nitrogen uptake and release in your tissues in real time. The two most common algorithm families take slightly different approaches. One type (based on the Bühlmann model) uses “gradient factors” you can adjust to add conservatism. Research has found that running this algorithm at its default settings can underestimate required decompression time for certain dive profiles, so dialing in more conservative gradient factors (lower numbers for the high gradient factor) provides a meaningful safety margin.
The other common type (RGBM-based, used in many Suunto computers) tends to prescribe adequate decompression time across a wider range of profiles in its default mode. Regardless of which computer you use, increasing the conservatism setting from the factory default is a straightforward way to build in extra protection. Never plan a dive right at the edge of your computer’s no-decompression limits.
Dive Enriched Air Nitrox
Breathing enriched air nitrox (typically 32% or 36% oxygen, compared to 21% in regular air) means you’re breathing less nitrogen at depth. Less nitrogen in your gas mix means less nitrogen dissolves into your tissues for a given depth and bottom time. In controlled studies comparing identical dive profiles, divers breathing nitrox produced fewer venous gas bubbles and experienced fewer DCS symptoms than those breathing air. At 40 meters, air divers showed both bubbles and DCS symptoms, while nitrox divers showed neither.
Nitrox does require certification and comes with its own risk: oxygen toxicity at greater depths. You’ll need to respect the maximum operating depth for your specific mix. But within those limits, nitrox is one of the most effective tools for reducing nitrogen loading.
Stay Hydrated Before You Dive
Dehydration thickens your blood and reduces circulation, making it harder for your body to transport dissolved nitrogen to your lungs for elimination. Animal research has shown dramatic results: pre-dive hydration reduced severe DCS from 47% to as low as 0% in a rat model, and increased the proportion of subjects with no DCS signs from 40% to 93%. In human studies, oral pre-hydration with an isotonic beverage significantly reduced circulating bubbles after a dive to 30 meters.
Drink water or a sports drink in the hours before diving. Avoid alcohol the night before, as it’s a strong dehydrator. Coffee in moderation is fine for most people, but supplement it with water.
Manage Your Body Temperature
Your thermal state during different phases of a dive has a real effect on DCS risk. Research shows the optimal approach is to stay cool during the bottom phase and warm during the ascent and decompression phases. Being warm at depth increases blood flow to your tissues, which drives more nitrogen into them. Being cold during ascent reduces blood flow, trapping nitrogen in tissues when you most need it to leave.
If you use a heated undergarment or active warming system, keep it at the minimum comfortable level while at depth and turn it up during your ascent and safety stop. In warm tropical water where you can’t control temperature, this is less of a factor, but cold-water divers with heated suits should pay attention.
Time Your Exercise Around Dives
Exercise done at the right time can help, but done at the wrong time it increases risk. Light to moderate aerobic exercise performed roughly 24 hours before a dive has been shown to reduce bubble formation. However, exercise done within about 10 hours before a dive, or more than 48 hours before, does not provide the same benefit. Exercising during or immediately after decompression increases circulating bubbles and interferes with nitrogen elimination. Avoid strenuous activity for several hours after surfacing.
Know Your Personal Risk Factors
Some people are more susceptible to DCS than others, even on identical dive profiles. Fatigue, poor fitness, obesity, age, and dehydration all raise risk. One significant anatomical factor is a patent foramen ovale (PFO), a small opening between the heart’s upper chambers that persists from fetal development. About 25% of adults have one. Divers with a PFO have 2.5 times the overall risk of DCS and four times the risk of neurological DCS, because venous bubbles that would normally be filtered by the lungs can cross directly into arterial circulation and reach the brain or spinal cord.
Routine PFO screening isn’t recommended for all divers, since the baseline DCS rate in recreational diving is low (about 3.6 cases per 10,000 dives). But if you’ve had more than one episode of DCS involving neurological, inner ear, or skin symptoms, testing for a PFO is worth discussing with a dive medicine specialist. Divers who know they have a PFO can still dive safely by using more conservative profiles: shorter bottom times, shallower depths, slower ascents, and longer safety stops.