Sleeping Gas

Sleeping gas is an oneirogenic general anaesthetic that is used to put a subject into a state where they are not conscious of what is happening around them. Incapacitating agent is a related general term for "knockout gases" or "KO gas" that ideally render a person unable to harm themselves or others, regardless of consciousness.

Most sleeping gases have undesirable side effects, or are effective at doses that approach toxicity.

Examples of modern volatile anaesthetics that may be considered sleeping gases are halothane vapour (Fluothane), methyl propyl ether (Neothyl), methoxyflurane (Penthrane), and the undisclosed fentanyl derivative delivery system used by the FSB in the Moscow theater hostage crisis.

The volatile anaesthetics noted above have odors. Odorless gases, e.g. methane (CH₄), carbon dioxide (CO₂) and carbon monoxide (CO), are a serious public health concern because people/animals may not be alerted to escape.

Possible side effects might not prevent use of sleeping gas by criminals willing to murder, or carefully control the dose on a single already sleepy individual. There are records of thieves spraying sleeping gases on campers, or in train compartments in some parts of Europe. Alarms are sold to detect and alert to such attacks, so a potential risk is believed by some people.

Fictional use of sleeping gas often involves stealth, as does criminal use of sleeping pills and poisons. In these works of fiction, sleeping gas is used by a character to incapacitate other characters. In some cases, science fiction or fantasy films depict the use of large quantities of sleeping gas to put large numbers of people to sleep. Suffocation is a concern even for non-toxic gases. To prevent in-home death, many countries require natural gas to have odorants added to the gas.