Other causes of oxygen deficiency include 
but are not limited to:

Acute respiratory distress syndrome
Carbon monoxide inhalation, such as that from a car exhaust and the smokes emission from a lit cigarette: carbon monoxide has a higher affinity than oxygen to the hemoglobin in the bloods red blood corpuscles, bonding with it tenaciously, and, in the process, displacing oxygen and preventing the blood from transporting oxygen around the body
Contact with certain chemicals, including pulmonary agents (such as phosgene) and blood agents (such as hydrogen cyanide)
Drowning
Drug overdose
Exposure to extreme low pressure or vacuum from spacesuit damage (see space exposure)
Hanging, whether suspension or short drop hanging
Self-induced hypocapnia by hyperventilation, as in shallow water or deep water blackout and the choking game
Inert gas asphyxiation
Congenital central hypoventilation syndrome, or primary alveolar hypoventilation, a disorder of the autonomic nervous system in which a patient must consciously breathe; although it is often said that persons with this disease will die if they fall asleep, this is not usually the case
Respiratory diseases
Sleep apnea
A seizure which stops breathing activity
Strangling
Breaking the wind pipe
Prolonged exposure to chlorine gas

Smothering
Smothering is a mechanical obstruction of the flow of air from the environment into the mouth and/or nostrils, for instance, by covering the mouth and nose with a hand, pillow, or a plastic bag. Smothering can be either partial or complete, where partial indicates that the person being smothered is able to inhale some air, although less than required.
In the UK, persons who are prescribed oral methadone can continue to drive after they have satisfactorily completed an independent medical examination which will include a urine screen for drugs. The license will be issued for 12 months at a time and even then, only following a favourable assessment from their own doctor. Individuals who are prescribed methadone for either IV or IM administration cannot drive in the UK, mainly due to the increased sedation effects that this route of use can cause. Mortality
In the United States, deaths linked to methadone more than quadrupled in the five-year period between 1999 and 2004. According to the U.S. National Center for Health Statistics, as well as a 2006 series in the Charleston Gazette (West Virginia), medical examiners listed methadone as contributing to 3,849 deaths in 2004. That number was up from 790 in 1999. Approximately 82 percent of those deaths were listed as accidental, and most deaths involved combinations of methadone with other drugs (especially benzodiazepines). Although deaths from methadone are on the rise, methadone-associated deaths are not being caused primarily by methadone intended for methadone treatment programs, according to a panel of experts convened by the Substance Abuse and Mental Health Services Administration, which released a report titled "Methadone-Associated Mortality, Report of a National Assessment". The consensus report concludes that "although the data remains incomplete, National Assessment meeting participants concurred that methadone tablets or Diskets® distributed through channels other than opioid treatment programs most likely are the central factors in methadone-associated mortality.