Undersea Hyperbar M
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Undersea Hyperbar M · May 2008
The effect of over- or underfilling the soda lime canister on CO2 absorption in two closed-circuit oxygen rebreathers.
O2 diving incidents investigated by our laboratory were related to improper filling of the soda lime canister in closed-circuit oxygen rebreathers. We studied the effect of overfilling or underfilling the canister on CO2 absorption using a continuous flow of 5% CO2. With a full canister in the Oxyger 57, CO2 began to rise at 130-160 min, reaching 1% at 240 min and 1.5% at 270 min. ⋯ For an excess of soda lime, moderate pressure was applied manually to achieve a full canister plus 300 g in the OxyNG 2. The initial rise in CO2 concentration started early, at 60 min with a full canister plus 300 g compared to 150 min with a full canister; 1% CO2 was reached at 120 min, compared to 210 min with a full canister. As the use of rebreathers becomes increasingly widespread in diving, close attention should be paid to proper filling of the soda lime canister.