Gaseous signaling molecules are gaseous molecules that are either synthesized internally (endogenously) in the organism, tissue or cell or are received by the organism, tissue or cell from outside (say, from the atmosphere or hydrosphere, as in the case of oxygen) and that are used to transmit chemical signals which induce certain physiological or biochemical changes in the organism, tissue or cell. The term is applied to, for example, oxygen, carbon dioxide, sulfur dioxide, nitrous oxide, hydrogen cyanide, ammonia, methane, hydrogen, ethylene, etc.
Select gaseous signaling molecules behave as neurotransmitters and are called gasotransmitters. These include nitric oxide, carbon monoxide, and hydrogen sulfide.
Historically, the study of gases and physiological effects was categorized under factitious airs.
The biological roles of each of the gaseous signaling molecules are outlined below.