A decompression chamber, also known as a re-compression or hyperbolic oxygen therapy chamber, is a device most commonly used in the world of scuba diving. It is a compartment where atmospheric pressure can be raised or lowered gradually. This allows divers and/or those who work underwater to readjust to normal atmospheric pressure after resurfacing from a dive rather than make decompression stops while still underwater.

As any good diver who paid attention to his basic training can tell you, underwater pressure is directly proportional to the increase in water depth. The deeper we go, the greater the atmospheric pressure. The greater the pressure, the more likely that the changing interplay of gasses will begin to come into play. There's a lot of physics involved in scuba diving, but the most important issue here is that increasing pressure correlates to increased absorption of nitrogen. The deeper you go, the more nitrogen enters your system. And too much nitrogen in your body for an extended period of time can lead to a lot of very bad things, including possible death. Of course there are other risks involved in an increase in atmospheric pressure but too much nitrogen is perhaps one of the most dangerous.

Divers combat this phenomenon by taking care to ascend slowly and also by making decompression stops along the way. This ensures that as our bodies acclimate to the decreasing pressure, the nitrogen bubbles do not become too large to exit our system and are safely expelled through proper breathing. However, some situations such as extremely choppy waters, predatory sharks, and grave injuries would deem a slow ascension and/or decompression stops highly dangerous, if not altogether impossible.

This is where the decompression chamber comes in. The presence of a decompression chamber is a very beneficial tool in ensuring diver safety, especially when diving in dangerous waters. Once out of the water, a decompression chamber is the only way a diver can safely change the atmospheric pressure around him, allowing him to normalize the levels of certain gasses in his system. This can potentially save his life from a lethal case of nitrogen narcosis (as well as a vast array of other pressure-related diseases, such as oxygen toxicity, decompression sickness, etc).

A decompression chamber is a staple in most scientific, technical, or otherwise professional diving charters. It can be found on certain navy vessels, a few large-scale dive liveaboards, and some hospitals. A decompression chamber may come in various sizes, but will always need to be big enough to enclose the whole body. It can be multiplace, a multi-person compartment or monoplace, a one person compartment; the former is preferred for more serious illnesses as it can fit both a patient and a nurse or doctor. When diving, it is always important to know where the nearest decompression chamber is, how to reach it, and how to contact its staff. The use of a decompression chamber should always be supervised by a knowledgeable and well-trained medical officer.