air vessel

A vessel, cell, duct, or tube containing or conducting air; as the air vessels of insects, birds, plants, etc.; the air vessel of a pump, engine, etc. For the latter, see Air chamber. The air vessels of insects are called tracheæ, of plants spiral vessels.

1. An enclosed volume of air which uses the compressibility of air to minimize water hammer.
2. An enclosed chamber using the compressibility of air to promote a more uniform flow of water in a piping system.