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any elastic aeriform fluid in which the molecules are widely separated from each other and so have free paths.
alveolar gas the gas in the alveoli of the lungs, where gas exchange with the capillary blood takes place.
blood g's the partial pressures of oxygen and carbon dioxide in blood; see blood gas analysis.
laughing gas nitrous oxide.
gas pains pains caused by distention of the stomach or intestines by accumulation of air or other gases. The presence of gas is indicated by distention of the abdomen, belching, or discharge of gas through the rectum. Gas-forming foods include highly flavored vegetables such as onions, cabbage, and turnips; members of the bean family; and fruits such as melons and raw apples. Some seasonings and other chemical irritants also produce gas.
tear gas any of various irritant vapors dispensed by aerosol and causing pain and severe lacrimation in humans; some also cause irritation of exposed mucous membranes as well as vomiting. Common ones include chloroacetophenone (CN), o-chlorobenzylidenemalononitrile (see CS), and dibenz(b,f)-1,4-oxazepine (see cr); the most common of the three is CS (also known as mace).