User:IntoCaves/sandbox/"Foul Air" in Caves

"Foul Air" in Caves, sometimes called "Bad Air", is an atmosphere which has a noticeable abnormal physiological effect on humans.

Limestone Caves

"In limestone caves, ‘foul air’ can be described as an atmosphere which causes a noticeable physiological affect on humans. Fouls air usually contains greater than 0.5% carbon dioxide (CO₂) and/or lower than 18% oxygen (O₂) by volume". Foul Air is not found in all caves, however if present, it is usually found in deep caves which have little air movement, thus increased concentrations of CO₂ and reduced O₂ can accumulate in the lower levels of the cave. An elevated concentration of CO₂ being the the most common foul air encountered in limestone caves which is threatening to human life, as opposed to reduced O₂ concentration.

Sources of CO₂ in Caves

There are a number of possible sources from which CO₂ can enter a cave and influence the composition of its atmosphere.

Naked Flame Test

The 'naked flame test' involves carrying a lit candle or lighting a match or cigarette lighter in the cave atmosphere. The behaviour of the burning flame or lack of flame, was erroneously used by cavers to determine the concentration of CO₂ in the atmosphere. The flame test is actually indicating the O₂ concentration which may indicate that the CO₂ is elevated. This becomes evident when considering the elements which are required for combustion to occur. ie. fuel, heat, oxygen.

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