Asphyxia is caused by a severe lack of oxygen to the body. If the lack of oxygen is prolonged or if no medical action is taken to combat the deficiency, then unconsciousness and death will occur. There are many different causes of asphyxia, most of which are accidental.

One of the most common reasons for asphyxiation is choking. A lump of food blocking the airways will cause asphyxia due to a lack of oxygen. The amount of time it takes to reach unconsciousness by this method is very rapid. Help can be provided through techniques such as the Heimlich Maneuver. In a number of cases however, the person is alone and unable to gain assistance.

Other very common deaths by asphyxia are drowning and inhalation of vomit. Inhalation of vomit has a very high incident rate among people who have alcohol or drug abuse problems. People can pass into unconsciousness and then begin to vomit. Because they are unaware of the event, they will begin to choke, and unless assistance is given, death can result.

Asphyxia can also be the result of strangulation. This may be accidental or deliberate. Asphyxia will occur very rapidly if a person constricts another person's airways by strangulation. Similarly, hanging is an extremely quick way to die by asphyxiation.

There is also chemical induced asphyxia. If chemicals such as carbon monoxide are inhaled, they will result in asphyxiation. A common suicide is death by carbon monoxide poisoning, the result of breathing car exhaust fumes in an enclosed area.

Any type of constriction to the chest or abdominal area can cause asphyxia. Severe pressure placed on these areas will make it very difficult for the person to breathe. Known as compressive asphyxia, this is a popular method of hand to hand combat used by the military.

An asthma attack can also bring about asphyxiation. Severe asthma attacks in which the sufferer is unable to use an inhaler have been known to end in death. Asphyxia has also been known to occur due to sleep apnea. Sleep apnea is a breathing problem that occurs during sleep. If the sleeper does not awaken when a blockage occurs, then the lack of oxygen will cause asphyxiation.

A number of deaths have occurred to divers due to asphyxia. The differential in the gas mixture that they breathe in shallow water can cause unconsciousness. In all cases of asphyxia that do not result in death, there is a severe risk of brain damage.