Which chemical is used to remove carbon dioxide in the BG4 breathing loop?

The chemical used to remove carbon dioxide in the BG4 breathing loop is Soda Lime. This compound is a mixture of sodium hydroxide and calcium hydroxide and functions effectively as a carbon dioxide scrubber. When carbon dioxide is exhaled, it comes into contact with the soda lime, which reacts chemically with the carbon dioxide to form sodium carbonate and water, thereby reducing the concentration of CO2 in the breathing loop. This process is crucial for maintaining breathable air during extended use of the BG4 apparatus in mine rescue operations.

Other options like Calcium Carbonate, Activated Charcoal, and Chemical Absorbent Gel do not serve this specific purpose effectively. Calcium Carbonate does not actively absorb carbon dioxide; rather, it can release CO2 when heated or treated. Activated Charcoal is primarily used for adsorbing volatile organic compounds and other gases but is not suitable for carbon dioxide removal. Chemical Absorbent Gel may serve various absorption roles but lacks the specific chemical reaction required to effectively remove CO2 from breathing air. Thus, soda lime is the standard choice for this function in respiratory equipment.