What type of supplied air respirators might explode if immersed in water?

Chemical oxygen generating units are specifically designed to produce breathable oxygen through a chemical reaction, often using materials that can be reactive in certain environments. When immersed in water, these chemicals can react violently, leading to combustion or even explosions. This makes them particularly hazardous when submerged.

In contrast, standard air supply units typically provide air from a tank that is not reactive with water. Diving air supplies are designed for underwater use and are constructed to be water-resistant and safe when immersed. Closed circuit systems recycle exhaled air, minimizing the introduction of external elements like water into the system, thereby avoiding the risk of explosion. Thus, while all the other options have specific safety features, chemical oxygen generating units lack this resilience with immersion in water.