Water's ability to extinguish Class A fires rests on its ability to cool the fuel and exclude oxygen. That is to say, water can remove two elements from the fire triangle discussed in section 2.6. More specifically, water excludes, or dilutes, oxygen by the formation of steam. Its high heat capacity accounts for its cooling ability. It can be sprayed a relatively long distance.
Carbon dioxide is suggested for fires involving delicate instruments and optical systems.
Never use carbon dioxide extinguishers against fires caused by lithium aluminum hydride or potassium. Carbon dioxide extinguishes Class B and C fires by depleting oxygen and cooling the fuel. It is nonconductive and therefore safe to use on electrical fires. It is delivered at an extremely low temperature and can cause thermal shock and create hairline cracks in circuit boards It can cause frostbite on contact with the skin. The MAP's diversity contributes to the fact it is the type most often found in homes and cars.