ABSTRACT
This chapter explores some of the ways that oxygen-deficient and oxygen-enriched atmospheres may be created in confined spaces. Oxygen-deficient atmospheres may occur in confined spaces as a result of ambient oxygen being: consumed by chemical reactions like oxidation (rusting and naturally occurring fermentation); displaced by inert gases like argon, carbon dioxide and nitrogen; and adsorbed by porous surfaces like activated charcoal. Oxygen may be consumed by industrial processes like welding, torch cutting and brazing that utilize open flames. Oxygen may also be consumed by fuel-fired space heaters that are used for comfort heating or to warm the air to the temperature required to cure some protective coatings. Space heaters require a certain amount of make-up air to replace that which is consumed by combustion. Oxygen may also be consumed by naturally occurring chemical reactions. Rusting and organic fermentation provide two classic examples of oxygen consumption by this mechanism.
