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Tuesday 26 July 2016


QI gas facts: how much gas does the average human produce?

A quietly intriguing column from the brains behind QI, the BBC quiz show. This week: QI’s all right now – in fact, it’s a gas.

Helium-filled balloons
Balloon-filler: Helium is one of the most common elements in the universe, making up 25 per cent of it Photo: Alamy

I have this one little saying: when things get too heavy, just call me helium, the lightest known gas to man. Jimi Hendrix

In a state

Most of us think of states of matter as a relatively stable division between solids, liquids and gases. In fact, there are now at least 16 different states and more keep being discovered.

Matter can take any of the following forms: a solid; an amorphous solid; a liquid; a gas; a plasma; a superfluid; a supersolid; degenerate matter; neutronium; strongly symmetric matter; weakly symmetric matter; Quark-gluon plasma; Fermionic condensate; Bose-Einstein condensate and strange matter.

The word “gas” was coined by a Flemish chemist, J B van Helmont (1577-1644), in the mid-16th century. It comes from the same Greek root as “chaos”.


Helium is a colourless, odourless, non-flammable gas. It is the second most common element in the universe, making up 25 per cent of it, but it is a very rare element on Earth, accounting for only one part in 186,000 of the Earth’s atmosphere.

The majority of the world’s helium supply comes from natural gas wells in western Texas.

In 2001, Ian Ashpole of Ross-on-Wye beat the world altitude record for a person tied to helium-filled party balloons. He flew to 11,000ft and then, as many of the 600 balloons began to pop, he had to parachute to safety.

If you inhale helium, your voice sounds higher because sound travels faster through it, and this increases the frequency, but not the pitch. For the opposite effect (a really deep voice) you can inhale xenon.

(The British Compressed Gas Association has written to us to point out that the inhalation of helium and other gases is potentially fatal, particularly for young people, and shouldn't be attempted under any circumstances.)


A crith (from the Greek word for barleycorn) is the mass of a litre of hydrogen with a temperature of 0C and at average sea level pressure.

In 1865, German chemist August Wilhelm von Hofmann proposed this as the standard unit of mass for all gases. Hydrogen is the simplest element and the only one whose basic form has no neutrons. It makes up three-quarters of the mass of the universe.


Ozone, an unstable “allotrope” or variant molecule of oxygen made of three oxygen atoms instead of two, was discovered in 1840 by the German chemist Christian Schönbein.

Investigating the peculiar odour that lingers around electrical equipment, he posited the existence of a distinct chemical substance, which he named after the Greek verb “to smell”, ozein. Jacques-Louis Soret identified this as the oxygen allotrope O3 in 1865.

Ozone, or “heavy air”, found favour with medical scientists still in the grip of the “miasma” theory of disease, where ill health was thought to spring from bad smells. Ozone, they thought, was just the thing to clear the lungs of harmful “effluvia” and the seaside was just the place to get it.

A whole industry grew up around “ozone cures” and “ozone hotels”. As late as 1939, Blackpool was still boasting “the healthiest ozone in Britain”.

Nowadays, we know that the seaside doesn’t smell of ozone – it smells of rotting seaweed. There’s no evidence this smell does you good or harm (it’s mostly compounds of sulphur). It may simply trigger positive associations in your brain, linking back to happy childhood holidays.

Conversely, real ozone is an irritant: it’s much more reactive than O2 and it’s potentially explosive.


Crisps are packed in nitrogen to protect them during transit. Oxygen would cause the oil to go rancid and the potatoes to go mouldy, and ambient air makes crisps go soggy; so packets are filled with nitrogen to keep the crisps fresh. Seventy-nine per cent of the air we breathe is nitrogen.


On average, we each produce about three pints of gas a day, released in 10-15 individual “episodes”, many of them while we sleep.

Most of the gas produced by the bacteria in our gut is hydrogen and CO2. The one that contributes most of the odour is hydrogen sulphide (H2S). This is usually present in very small concentrations (less than 0.5 per cent), but it is so potent that our noses can detect it in concentrations of 0.0047 parts per million.

As for methane (CH4), most humans can’t produce it at all. Methane in the body results from microbes called methanogens, which are not bacteria but members of the Archaea kingdom, the oldest life forms on the planet. Only about one-third of humans have methanogens among their gut flora.

No one knows exactly why, though it appears to be genetically determined. A child of two methane-producing parents is 95 per cent likely to produce a methane-generating child.


Smelling salts give off ammonia gas (NH3) which irritates your nose and lungs and triggers the inhale reflex – which will wake you up if you faint. Older names for it include sal volatile and salt of hartshorn – because before ammonia could be synthesised, it was extracted from the horns of male deer.

The new 'K’ series of QI is now running at 10pm Fridays on BBC Two. 'The Secret Museum' by Molly Oldfield' (HarperCollins) is available from Telegraph Books (0844 871 1515)

Next week: QI’s crustacean nation

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