Nitrox for UK Divers: When Enriched Air Makes Sense (And When It Doesn't)
Complete nitrox guide for UK divers: benefits in cold water, certification costs, when to use enriched air, and equipment requirements for British diving.
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Take Our QuizEnriched Air Nitrox. EAN32. EAN36. The yellow and green tanks you see at dive sites. More expensive than air. Worth it?
For UK wreck diving, absolutely. For shallow reef diving, debatable. Here's when nitrox makes sense.
What is Nitrox?
Standard air: 21% oxygen, 79% nitrogen. Nitrox: Higher oxygen (typically 32% or 36%), lower nitrogen.
Breathing higher oxygen means absorbing less nitrogen for a given depth and time. Lower nitrogen loading means longer no-decompression limits and lower DCS risk.
The tradeoff: Higher oxygen has maximum operating depth limits. Exceed your MOD and you risk oxygen toxicity (convulsions, potentially fatal).
Nitrox for UK Wreck Diving
Example: SMS Markgraf wreck at 40m depth.
Air NDL at 40m: 9 minutes EAN32 NDL at 40m: 15 minutes
That's 67% more bottom time. On a 45m wreck costing £100 boat fee, every minute matters.
Cold water increases DCS risk 50-100% compared to tropical. Nitrox's reduced nitrogen loading provides safety margin UK divers need.
Repetitive diving (typical UK weekend: 4-6 dives over 2 days) builds nitrogen loading. Nitrox reduces cumulative loading significantly.
When Nitrox Doesn't Help
Shallow diving (12-20m): NDLs are already long. Farne Islands seal diving at 15m depth gives 80+ minute NDL on air. Nitrox adds little.
Single dives: If you're doing one dive per day, nitrogen loading isn't a concern.
Budget diving: Nitrox fills cost £6-10 vs £5 for air. Over dozens of dives, adds up.
Sites without nitrox: Not all UK dive centers offer it (though most do now).
EAN32 vs EAN36
EAN32 (32% oxygen): Standard for UK wreck diving. MOD 34m (safe to 40m emergency). Widely available. Suits 20-40m depth range (most UK wrecks).
EAN36 (36% oxygen): Better for shallow diving 12-28m. MOD 28m. Less commonly available. Suited for reef diving, seal encounters, shallow wrecks.
For Scapa Flow and deep wrecks: EAN32 is standard. For Farne Islands and shallow sites: Air is often adequate.
Equipment Requirements
EAN32-40: Uses standard recreational scuba equipment. No modifications needed. Your regulator, BCD, dive computer work normally.
Above 40% oxygen: Requires oxygen-cleaned equipment (technical diving territory, not recreational).
Dive computer MUST support nitrox: Set gas mixture before diving. Computer calculates NDL based on actual gas. Using air settings on nitrox is dangerous (computer will allow you to exceed safe limits).
Modern computers (Shearwater, Suunto, Garmin, even budget Mares/Cressi) support nitrox. Older computers may not. Check before buying.
Certification Requirements
PADI Enriched Air Diver: £150-250, includes online learning and in-person session (4-6 hours). No dives required (academic course).
BSAC Enriched Air Nitrox: £100-180 through clubs. Similar content, internationally recognized.
SSI Enriched Air Nitrox: £120-200.
Courses cover: oxygen physiology, CNS oxygen toxicity, MOD calculations, equipment considerations, gas analysis procedures, dive planning with nitrox.
Most courses complete in one day or two evenings. One-time cost providing lifetime benefit.
Gas Analysis
Before EVERY dive, you must personally analyze your nitrox tank. Never trust the label. Errors happen (wrong gas, partial fills, mislabeling).
Process: Use oxygen analyzer at dive center. Record percentage. Calculate MOD. Set dive computer to analyzed percentage (not nominal). Sign analysis log.
MOD formula: (1.4 ÷ oxygen fraction) × 10 - 10 = MOD in meters
Example: EAN32 (0.32 oxygen fraction) MOD = (1.4 ÷ 0.32) × 10 - 10 = 33.75m
Round down for safety: 33m MOD.
Cost-Benefit Analysis
Nitrox certification: £150-250 one-time Nitrox fills: £6-10 vs £5 air (+£1-5 per dive)
Scapa Flow trip (8 dives): +£8-40 for nitrox Benefit: 30-50% longer bottom time on deep wrecks, reduced DCS risk in cold water
For regular UK wreck divers (20+ dives/year at 25m+), nitrox certification pays for itself through safety and extended bottom time. For casual divers or shallow-only diving, less compelling.
Safety Considerations
Never exceed MOD: Oxygen toxicity causes convulsions. Underwater convulsion = drowning. Respect MOD religiously.
Monitor CNS oxygen exposure: Long/deep nitrox dives accumulate CNS oxygen loading. Dive computers track this. Stay within limits.
Nitrox doesn't eliminate DCS risk: Reduces it, doesn't remove it. Still follow safety stops, slow ascents, conservative profiles.
Cold water + nitrox: Excellent combination. Nitrox offsets cold water's increased DCS risk. Use conservative computer settings anyway.
Practical Advice for UK Divers
Get certified: £150-250 investment opens up nitrox use for entire diving career. Worth it for anyone planning regular UK wreck diving.
Use EAN32 as standard: For 20m+ wrecks. Default choice for Scapa Flow, South Coast wrecks, any dive deeper than 25m.
Stick with air for shallow: Farne Islands, quarry training, shore dives under 20m. Air is adequate and cheaper.
Always analyze: Never skip gas analysis. Ever. Your life depends on knowing what's in your tank.
Set computer correctly: Wrong gas setting on computer can kill you. Double-check before every dive.
Nitrox isn't magic. It's a tool. For UK deep wreck diving, it's an extremely valuable tool. For shallow UK diving, it's optional at best.
Products Mentioned in This Guide
Shearwater Peregrine
Shearwater
The sweet spot for UK diving. Brilliant colour display readable in murky water, user-replaceable battery for cold condit...
View on AmazonSuunto Zoop Novo
Suunto
Reliable entry-level computer with clear display and conservative algorithm. Perfect for new UK divers building experien...
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Start the QuizFrequently Asked Questions
Is nitrox worth it for UK diving?
Yes, for certain UK diving profiles. Nitrox extends bottom time on deeper UK wrecks (30-40m common at Scapa Flow, South Coast), reduces nitrogen loading in cold water (DCS risk is higher in cold water), and provides safety margin for repetitive dives. Example: diving the SMS Markgraf wreck at 40m on air gives 9-minute NDL, while EAN32 gives 15 minutes (67% longer). For shallow reef diving (12-20m), the benefit is minimal. Nitrox certification costs £150-250 and pays for itself after 10-15 deep dives. UK operators increasingly offer nitrox fills (£6-10 vs £5 for air). Worth it if you regularly dive deeper than 25m or do multi-day dive trips. Not essential for casual recreational diving or inland quarries.
What percentage nitrox should I use in the UK?
EAN32 (32% oxygen) is standard for UK diving: provides benefit at 20-40m depths (typical UK wreck range), widely available at UK dive centres, and safe maximum operating depth of 34m (40m emergency). EAN36 (36% oxygen) suits shallower diving 12-28m with maximum depth 28m, useful for extended reef dives but less common at UK operators. Never dive deeper than your MOD (maximum operating depth): EAN32 beyond 34m risks oxygen toxicity. Most UK dive computers allow you to set gas mixture; always analyse your tank and set computer before diving. For Scapa Flow wreck diving, EAN32 is near-universal. For Farne Islands reef diving, air is often adequate. Always carry nitrox certification card even if diving air.
Do you need special equipment to dive with nitrox?
Equipment requirements depend on oxygen percentage: EAN32 to EAN40 (up to 40% oxygen) can use standard recreational scuba equipment without modification. Your regulator, BCD, and dive computer work normally. However, you MUST have a nitrox-compatible dive computer or use nitrox tables (air computers will give incorrect NDLs). Tank must be nitrox-clean and clearly marked with contents and MOD. Above 40% oxygen requires oxygen-cleaned regulators and dedicated equipment (technical diving). UK recreational diving uses EAN32/36 exclusively, so standard equipment works. Ensure your dive computer has nitrox capability (most modern computers do; older computers may not). Budget dive computers like Suunto Zoop Novo and Mares Puck Pro support nitrox. Check before buying.
How much does nitrox certification cost in the UK?
PADI Enriched Air Diver: £150-250 depending on location and operator, includes online learning, in-person session (4-6 hours), and certification. No dives required (academic course only). BSAC Enriched Air Nitrox: £100-180 through clubs, similar content, recognized internationally. SSI Enriched Air Nitrox: £120-200. Courses cover: oxygen physiology, CNS oxygen toxicity, MOD calculations, equipment considerations, gas analysis, and dive planning. Most certifications complete in one day or split over two evenings. Required for nitrox diving at all UK operators. Many combine nitrox certification with Advanced Open Water or Wreck Diving specialty. One-time cost that adds value for entire diving career, particularly for UK wreck diving where depth and repetitive dives make nitrox extremely beneficial.
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