Fun in the decompression chamber
Dry dive sessions offer nitrogen as alternative to alcohol
A trip to the decompression chamber should only occur on a bad day… unless you’ve been shut inside for fun.
The London Diving Chamber is located at the Hospital of St John and St Elizabeth in swanky St John’s Wood. Roughly the size of a van and equally white, it exists primarily for the treatment of bent divers and burns victims.
But a ‘dry dive’ offers the opportunity to enter and experience heavy narcosis under controlled conditions – a good idea from a safety perspective. It also happens to be a fun way to spend a Thursday evening.
A friendly Antipodean chamber attendant greets the group, talks us through the basics and directs all six divers to change into scrubs; in a rich oxygen environment what can be allowed inside the pot is strictly controlled for fear of fire. Computers can be brought along but must be left inside a bucket of water for the duration. We sit on benches either side, a second attendant enters to oversee the session and closes two doors, the external ‘airlock’ style, and then inner.
down to 50 metres… soon we’re all chuckling
Counter-intuitively, there’s no locking mechanism required: the pressure inside keeps the chamber door firmly sealed.
The clock is running. Wearing a pair of defenders, there’s a fierce hissing sound and I feel a squeeze on my ears. The inrushing air is surprisingly warm and our attendant advises drinking plenty of water throughout the session – this helps keep us hydrated and makes equalising easier. My problematic right ear takes a bit of working but within 5 minutes we bottom out at 50 metres.
Clearance diver Tony Groom once remarked that for him narcosis was never much of a problem, only causing “pins and needles in his hands”, where others might become completely incapacitated. Being in the chamber seems to verify this person-by-person observation: for me, I get a case of the sweats and stupefying drunkenness; two others appear pretty out of it. The rest are doubled up in peals of laughter! Soon we’re all chuckling.
Pens and paper are handed out to repeat a simple test done outside: to circle every letter ‘L’ in a piece of text in a minute. Scores on average are a third poorer when ‘narked’. Nobody has ever scored higher second time around a staff member clarifies later, although some hardcore nitro-heads manage to stay close to parity.
One effect of breathing air under compression is a ‘chipmunk’ style squeaky voice, and I struggle to ask the attendant sensible questions about barometric science while sounding so ridiculous. Or maybe I’m just too narked to take in the answers.
Oxygen masks are clipped in and donned for the return to the surface. Warm air is replaced by chilly as we ascend to 9 metres for 3 minutes, then 6 metres for 23 minutes. All of the air being pumped in and out of the chamber is actually at the same temperature; it’s the pressure differential that excites molecules causing this effect.
After a total dive time of 47 minutes the session is over. Masks off, photographs taken and we exit, with a second group waiting to enter. The chamber is a valuable tool and earning its keep tonight. Should I ever need to enter it again, the experience will probably not be so entertaining.
Everything you wanted to know about scuba kit but were afraid to ask
Indispensable guide to wreck diving in this remote Pacific atoll