Asphyxia or asphyxiation is a condition of severely deficient supply of oxygen to the body. In order to be considered torture asphyxia should not be caused by natural causes or by any incidental means.

Causes of forced oxygen deficiency considered torture usually are:
Strangling - using hands, rope, ecc... to suffocate someone for a period of time
Drowning - forcing someone to keep head underwater for a period of time
Hanging - forcing someone to hang for a period of time
Gas intoxication - forcing someone to inhale gas for a period of time

Extended asphyxia can lead to death.