Abstract: A gas demand device cycles through five successive operation phases: gas is prevented from flowing through the timing gas and demand gas flow paths; gas is allowed to flow through the timing gas flow path and gas is prevented from flowing through the demand gas flow path; gas is allowed to flow through the timing gas and demand gas flow paths; gas is prevented from flowing through the timing gas flow path and gas is allowed to flow through the demand gas flow path; and gas is prevented from flowing through the timing gas and demand gas flow paths.

Abstract: A pneumatic oxygen conserver delivering a constant minute flow volume rate to a nasal mask, face mask, or nasal cannula is rendered lightweight by using tubing connected between the conserver and an oxygen source as a reservoir of oxygen for delivery to the nasal mask, face mask, or nasal cannula.

Abstract: A gas demand device includes a primary chamber, a slave chamber, a secondary slave chamber, a timing gas flow path and a demand gas flow path all formed in a main body. The device cycles through five successive phases of operation in which: 1) a main diaphragm and a slave diaphragm are closed to disallow gas to flow through the timing gas and demand gas flow paths, 2) a main diaphragm is open while a slave diaphragm is closed to allow gas to flow through the timing gas flow path and disallow gas to flow through the demand gas flow path, 3) the main and slave diaphragms are open to allow gas to flow through the timing gas and demand gas flow paths, 4) the main diaphragm is closed while the slave diaphragm is open to disallow gas to flow through the timing gas flow path and allow gas to flow through the demand gas flow path, and 5) the main and slave diaphragms are closed to disallow gas to flow through the timing gas and demand gas flow paths.