I would like to make a suggestion for caves that also exists in real life.
Cave climbers and explorers must always be very careful with the gases that do or do not occur in caves. They used to take fire down with them. As soon as the fire went out, they knew that the oxygen concentration was too low and they would suffocate if they stayed there. The first hard hat was also equipped with a candle. Not just for the light, but mainly as a safety measure because of the gases.
Just a natural enemy.