Non-hygroscopic soda lime is used to remove exhaled carbon dioxide (CO2) in closed circuit breathing apparatus. As a diver exerts him/herself while swimming, the soda lime in the scrubber canister will gradually be used up until it is no longer capable of absorbing more CO2. This results in the dangerous medical condition of hypercapnia (abnormally high CO2 concentration in the body). The present invention uses a microcontroller and sensors to continuously monitor the rate of soda lime usage and calculates the available remaining dive time. The remaining time (in hours and minutes), continuously adjusting for changes in physical activity, is presented to the diver via his/her dive computer display or a display in the facemask. Importantly, the system’s memory allows the diver to use the equipment for repeat dives, relying on yet unused CO2 absorbing capacity. More