WE ARE THE MOUSE IN THE JAR WITH THE CANDLE

If you take a large bell-jar, put a lighted candle and a mouse in, then put the cork on, after a while the mouse will keel over and die, because the burning candle will have consumed so much oxygen that the mouse will be asphyxiated.

Burning oil and coal does the same to the earth, but it takes longer because the earth is a big jar and there are plants making oxygen. But, slowly, slowly, slowly, as we keep burning the Black Stuff and bumping off plants we are reducing the percentage of oxygen in the air. So far, the coal boys assure us, we have reduced it only .03%. But the more carbon-dioxide there is the less oxygen there is, and the level of carbon-dioxide is rising at an accelerating rate, so the level of oxygen is decreasing likewise.

When do we start worrying? The section on this page headed 'Physiology of Asphyxiation' shows that degrees of asphyxia start surprisingly early. Even at 20% of oxygen by volume you get 'dimunition of physical and intellectual performance.'

The US safety body, OSHA, can shut down a public building if the level of oxygen in it drops only 1%. And OSHA rules say that miners and other people who work underground or in confined spaces must wear safety gas-alarms that will sound off for evacuation at 'the hazard level of 19.5% oxygen.' At sustained levels of 16.5% (about the concentration in the air you breathe out), we can die from asphyxiation.

This page gives all the OSHA regulations, and includes this paragraph: 'Oxygen deprivation is one form of asphyxiation. While it is desirable to maintain the atmospheric oxygen level at 21% by volume, the body can tolerate deviation from this ideal. When the oxygen level falls to 17%, the first sign of hypoxia is a deterioration to night vision which is not noticeable until a normal oxygen concentration is restored. Physiologic effects are increased breathing volume and accelerated heartbeat. Between 14-16% physiologic effects are increased breathing volume, accelerated heartbeat, very poor muscular coordination, rapid fatigue, and intermittent respiration. Between 6-10% the effects are nausea, vomiting, inability to perform, and unconsciousness. Less than 6%, spasmatic breathing, convulsive movements, and death in minutes.'

It is therefore not a good idea take much oxygen out of the atmosphere. Below 20% none of us can function at our best, at 19/5% the hazard starts in earnest, and every 1% drop below that is a really bad idea. The risk is increased if the displacing gas is carbon-dioxide, because increased carbon-dioxide levels in the body compound the effect of reduced oxygen by messing up our respiratory reflex, which is controlled by the level of carbon-dioxide.

If we were to burn all the 1980 billion tonnes of coal known to exist in the world, we would remove about 3% of the oxygen. Then there is the oil on top of that...

The earth is a big jar, but we need to snuff that candle.