Are the caves so cool because there are air conditioners inside them? There are a large number of visitors every year who ask that question. It surprises them that during a hot summer day the caves are a comfortable 17 degrees Celsius. During a cold winter day the surprise is that the caves are so much warmer than outside, a cozy 17 degrees Celsius. The caves stay close to the same temperature all the year round. The reason is that the surrounding rock is quite massive and an enormous amount of heat is needed to change its temperature. As air flows through a cave it comes in contact with the wall and, depending on the time of year, either warms or cools and hence ends up an even 17 degrees Celsius. Most caves exhibit the same phenomena although the temperature that they stabilise at will vary depending on what the average temperature is of the area they are in.

Understanding about the stable air temperature in the caves helps to understand why there is always fresh air despite large numbers of visitors passing through the caves. As visitors pass through they exhale carbon dioxide. If there was no air flow the carbon dioxide would collect in the cave and eventually it would become stifling. It would also start to corrode the formations. Fortunately we are helped by the fact the hot air rises.

During the winter months the air inside the caves is warmer than that outside. The air flows up and out of the cave. Since there are several entrances to the caves, the air flows out of the higher entrances and sucks cold air in through the lower entrances. The cold air that is drawn in is then warmed up, flows through the cave collecting the carbon dioxide and replacing it with oxygen. Eventually the air floats up and out through an upper entrance. The cycle continues, replacing the stale air.

During the summer months the opposite happens. During these months the air inside the caves is cooler than outside and hence it sinks and flows out a lower entrance. This draws in warm air through an upper entrance and hence another air cycle is created. Since it is very rare that the temperature outside will be exactly the same as that inside the caves, there will almost always be an air flow occurring to flush the caves of stale air.

Other atmospheric conditions will also contribute to air flow. Changing air pressure is a significant factor, especially where the cave only has one entrance. Think of a cave as being like a big plastic bottle. If you blow into a bottle the air inside will compress and assume the same pressure as that outside, i.e.. inside your mouth. As soon as you take the bottle away from your mouth, the pressure outside the bottle drops and a small rush of air occurs coming out of the bottle. Returning to the cave, air pressure is always changing. If the air pressure outside the cave increases, it forces more air into the cave. As the air pressure drops, the air that is stored inside the cave starts to rush back to the surface, causing a breeze.

Breezes are one way in which cave explorers find new caves. As they crawl around inside a cave they try and sense gentle breezes. Sometimes they will light a candle to see if the flame flickers in a breeze which is too faint to feel. If they find a breeze it often means there is a passage nearby that connects to other passages that are large enough to contain lots of air that responds to changes in air pressure.