Magnesium, potassium, sodium titanium, alkyllithiums, Grignards, and diethylzinc are extremely combustible and must be used with caution and appropriate safety measures. These chemicals react violently with water, air and other chemicals and cause class D fires which burn at high temperatures. At such, typical fire extinguishers are not sufficient for this type of fire.
D Fire Extinguishers contain sodium chloride or graphite metal-based powder. When discharge on a fire, the heat causes the powder to cake and form a crust which excludes air and dissipates the heat.