Exposure to Trace Gases

Because the chamber is an enclosed environment, it is possible that other gases that may be toxic could build up. CO₂ is produced by the patient and tender, and significant accumulation in the atmosphere may result in an increase in PaCO₂ , which may augment nitrogen narcosis as well as CNS O₂ toxicity. The chamber atmosphere must therefore be carefully monitored and action taken to lower individual gas concentrations if threshold limits are exceeded. Most hyperbaric facilities require that atmospheric PCO₂ not rise above 4 mm Hg. Other potentially toxic gases may be produced from smoldering or burning of electrical components or may be released from batteries. All batteries produce small quantities of hydrogen. Lithium-sulfur dioxide batteries, though hermetically sealed with an interior pressure of 4.5 ATA, may vent sulfur dioxide in the event of seal failure. (Minimization of these risks is discussed later.) CO is released into the atmosphere in a closed chamber by body metabolism and other environmental factors and, during saturation dives (prolonged chamber exposure at a constant pressure), may accumulate unless converted to CO₂ by catalysis. Because monoplace chambers are continuously ventilated with 100% O₂ at high flow rates, this issue pertains only to multiplace chambers used for deep saturation exposure.