It's absolutely true: pure oxygen can give rise to feelings of euphoria. Not for the people who inhale it from oxygen vending machines - which, as reported this week, are now being tested in nightclubs - but for the people who sell it.
The cheapest way to breathe oxygen is to breathe air - at the time of going to press, it's still free - but even manufactured oxygen, at source, is dirt cheap. Pure Oxygen Ltd, based in London, will send you an eight-litre canister of 99.5% pure oxygen through the post for £11.99. If you think that's a bargain, consider this: BOC charges £3 for 300 litres of pure oxygen. That would keep you going for almost an hour. Your eight-litre can will give you about 80 breaths, tops.
Even by the mark-up standards set by bottled water companies, the leisure and lifestyle oxygen vendors are doing well. The machine that made the news this week - at the Here and Now nightclub in High Wycombe - gives you up to 10 minutes of 40% pure oxygen in three bursts for £3.50, according to Steve Dennis of Luminar Leisure, which owns the club. That's a lot for mildly souped-up air.
Dennis said clubbers were being offered the oxygen "for the price of a pint of lager". He denied reports that Luminar had decided to roll out the machines across the hundreds of clubs it owns, but said: "If this machine gives a worthwhile profit margin, produces happy customers and doesn't harm their health, and there's a demand, we'll take it." If Luminar is selling lager at £3.50 a pint it is clearly setting the profit bar high - but oxygen seems well-placed to meet its hopes on that score.
Oxygen has hardly reached the status of a craze in the UK, as it has in the far east, where it comes in strawberry flavour at oxygen bars. There are machines here at some gyms, and there's one next to the juice bar at Harvey Nichols in London, where for a comparatively modest tenner punters can inhale for a month (for 10 minutes at a time). The publicity of oxygen has definitely increased. But is it any good?
Oxygen is certainly essential to life. The air that you normally breathe is 20.9% oxygen (the rest is mainly nitrogen). Your lungs absorb about a quarter of that oxygen and transmit it to the blood, which in turn carries it to all the cells of the body, where it is used in chemical reactions to provide the energy that keeps you alive. A catastrophic failure of the blood supply, in a heart attack or a stroke, is not dangerous because of the blood itself, but because of the oxygen the blood no longer transports.
The logic of the vendors of oxygen as a lifestyle drug (and it is technically classified by the Medicines Control Agency as a drug) is clear, but not necessarily valid. It goes roughly like this: oxygen is vital to life; life is good; air only has 21% oxygen; so double the oxygen, and life is twice as good.
That's all very well, but millions of years of evolution mean that, in normal circumstances, are pretty comfortable with our 21%/79% oxygen/ nitrogen mix. It's not that breathing a more oxygen-rich mixture will harm us (although after six hours, pure oxygen does become toxic for healthy people). It's just that there's not much we can do with the extra gas. Like vitamin C tablets, once the body has absorbed its daily needs, there's no point in pumping more in.
Decades of research have come up with no evidence that breathing pure oxygen makes healthy subjects intoxicated, euphoric or energetic. They may think that what they are breathing through their mouths is pepping them up, but maybe that's because they've paid through the nose. Studies suggest that when people don't know whether they're breathing air or oxygen, they can't tell the difference.
That doesn't mean pure oxygen isn't useful when regular air is thin - such as at the top of Mount Everest - or polluted. The popularity of oxygen bars in Tokyo and Bangkok is linked to the cities' notorious smog; Los Angeles, another city where the oxygen bar has flourished, is also smoggy.
The Russian Arctic, where the Soviet Union built mad industrial cities, was famed for the "oxygen cocktails" it used to offer workers. Less well known, until glasnost, was the hideous scale of the pollution that the oxygen cocktails were intended to combat.
Concentrators are available on prescription. But Pure Oxygen is working on another level. Its website urges you to send away for one of its £11.99 canisters if you answer "yes" to one of the following questions: "Do you wake up tired, even after eight hours of sleep? Do you sleep restlessly, waking up frequently? Do you suffer from chronic fatigue? Do you have poor physical endurance? Do you tend to be moody and irritable? Are you susceptible to colds and the flu? Do you suffer from allergies? Do you frequently feel tense and on edge? Are you frequently constipated? Do you have frequent pain in the shoulders and/or back? Do you have weight problems? Do you crave sweets, alcohol or soda?"
That seems to cover just about everyone. But even David Hardoon, Pure Oxygen's director, was sceptical about oxygen in nightclubs. "It's the quality of air. It can be very stuffy and smoky in the clubs, and people just feel a little bit more refreshed when they take oxygen. Our products are for more serious purposes, when for one reason or another people have got a lack of oxygen, to do with breathing problems, or pollution, or travelling on the underground."
Dr Donald Miller, a lecturer in anaesthetics at King's College London, said he couldn't imagine that breathing pure oxygen for a short time would do a healthy person any harm, or any good, although it might enable them to hold their breath for longer. Dr Vinay Patroe, an anaesthetist working for BOC, agreed. "The benefits to a fit person of breathing pure oxygen are very unclear. And when I say unclear, I'm being charitable. There's no evidence to suggest any benefit, or indeed any difference - certainly not from 10 minutes every half-day."
The fact is that unless people are in a hermetically sealed space, the proportions of oxygen and nitrogen in the air remain pretty much the same. The only advantage to breathing pure oxygen is the same as breathing pure air: the pollutants are removed. Clubbers who are willing to pay large sums to dance in a hot, sweaty, crowded space, and then pay further large sums to the club proprietor in order to breathe clean oxygen, may indeed be suffering from something. But it is not something that oxygen can cure.