Alkali metals (e.g., sodium and potassium) react violently with water and decompose the water, giving off hydrogen, which may be ignited by the heat of reaction. This is similarly true for alkaline earth metals (calcium and magnesium). Alkali metals can also ignite spontaneously in air, especially when the metal is in powdered form, and/or the air is moist. Alkali metals should be stored under mineral oil or kerosene. Avoid using oils containing sulfur since a hazardous reaction may occur. Use only special, dry powder fire extinguishers on alkali metal fires. Any waste alkali metals should be placed in labeled, leak-proof container, covered with mineral oil and disposed of via the DESHS. Finely powdered metals (e.g. Al or Fe) that come in contact with acids may ignite and burn. Metal powders can also create a dust explosion hazard when the powders become airborne in an area where a spark or flame is present.
Mercury is a virulent poison and is readily absorbed through the respiratory tract, the gastrointestial tract, or through unbroken skin. It is therefore imperative that it not be touched, or its vapors inhaled. It acts as a cumulative poison (like arsenic) since only small amounts of the element can be eliminated at a time by the human organism. The vapor pressure of mercury is quite high; air saturated with mercury vapor at 20°C contains a concentration that exceeds the toxic limit more than 100 times. Therefore mercury should only be used in a well-ventilated hood. Mercury spills must be immediately covered with sulfur to bring down the vapor pressure (see section on chemical spills).