Air Currents

Cave tourVisitors frequently ask if the cave will ever run out of oxygen or if noxious gases like methane or carbon dioxide can build to the point of toxicity. In Crystal Cave the answer is NO! Most caves are very well ventilated and Crystal Cave is no exception. The cave is ventilated by exchanging air with the outside. This process is accomplished through the changing barometric pressure. Outside the cave, air is warmed during the day. As it warms it becomes less dense and the barometric pressure falls. When the outside pressure falls, the air flows out of the cave. At night the air is cooled, becoming more dense causing the pressure to rise. Air will be drawn into the cave during the night. Other pressure changes are related to the weather like those changes which accompany the passage of a storm front. These pressure changes are superimposed upon the daily fluctuation. The cave pressure adjusts to conform to the resultant effect of both.

Temperature will also affect air movement. If the cave air is colder (more dense) than the outside, as in summer, the air will flow out of the cave through the lower Tree Fork Entrance into the gully, pulling warmer air in through the upper Service Entrance. If the cave air is warmer (less dense) than the outside air as in winter, air flow will be upward and out the upper Service Entrance and colder air will be pulled in through the lower Tree Fork Entrance. This type of air flow is similar to the “Chimney Effect”.

The cave air is in constant motion as it attempts to adjust to surface changes. Usually these air currents are so slow that they can be detected only with barometers or very sensitive wind gauges. However, there are times when the air currents are quite obvious as light breezes and strong gusts moving through the Cave Door and the store’s stairwell.

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