Hydrogen cyanide in the context of "Gas chamber"

Organic compounds are a subclass of chemical compounds of carbon. Little consensus exists among chemists on the exact definition of organic compound; the only universally accepted definition is the quasi-tautological "organic compounds are the subject matter of organic chemistry".

Generally, any large chemical compound containing a carbon–hydrogen or carbon–carbon bond is accepted as an organic compound. Thus alkanes (e.g. ethane, CH₃−CH₃) and their derivatives are typically considered organic. For historical and disciplinary reasons, small molecules containing carbon are generally not accepted: cyanide ion (CN), hydrogen cyanide (HCN), chloroformic acid (ClCO₂H), carbon dioxide (CO₂), and carbonate ion (CO2−3) may all be excluded.

Hydrogen sulfide (preferred IUPAC name and American English) or hydrogen sulphide (Commonwealth English) is a chemical compound with the formula H₂S. It is a colorless hydrogen chalcogenide gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.

Hydrogen sulfide is toxic to humans and most other animals by inhibiting cellular respiration in a manner similar to hydrogen cyanide. When it is inhaled or its salts are ingested in high amounts, damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death. Despite this, the human body produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule.

Triatomic molecules are molecules composed of three atoms, of either the same or different chemical elements. Examples include H₂O, CO₂ (pictured), HCN, O₃ (ozone) and NO₂.

Smoke is an aerosol (a suspension of airborne particulates and gases) emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires (including stoves, candles, internal combustion engines, oil lamps, and fireplaces), but may also be used for pest control (fumigation), communication (smoke signals), defensive and offensive capabilities in the military (smoke screen), cooking, or smoking (tobacco, cannabis, etc.). It is used in rituals where incense, sage, or resin is burned to produce a smell for spiritual or magical purposes. It can also be a flavoring agent and preservative.

Smoke inhalation is the primary cause of death in victims of indoor fires. The smoke kills by a combination of thermal damage, poisoning and pulmonary irritation caused by carbon monoxide, hydrogen cyanide and other combustion products.