Just like toxicity, magnesium metal has safety applications. For example bulk magnesium must be heated to near its melting point. Because of its high thermal conductivity, which keeps solid forms of magnesium such as castings or fabricated parts from developing severe hot spots, these forms constitute no fire hazard unless caught in a serious fire of other combustible materials. Risks associated with dry blasting, grinding, sanding, polishing, and buffing operations fines are minimized by collection in approved wet dust collectors, good housekeeping measures to avoid dust accumulation, elimination of spark or flame sources, and proper handling and disposal of collector sludge.
Magnesium has one main safety side - protection for the atmosphere. The choice depends on the nature of the fire. If the fire is small and the burning castings are readily accessible, they should be removed from the furnace to a steel container and covered with a commercially available fire-extinguishing powder intended for use with magnesium. When the fire is such that neither of the above methods can be used for extinguishing it, another method is the use of boron trifluoride (BF3) or boron trichloride (BCl3), both of which are available as bottled gases. As with the other methods, all power, fuel, and protective-atmosphere lines should be shut off.
If the heat-treating furnace fire includes more than several hundred pounds of magnesium parts, is well advanced prior to discovery, involves a large pool of metal on the floor of the furnace, or is in a furnace with excessive air leaks, these gases cannot be expected to extinguish the fire completely. Dry cast iron chips graphite powder combined with heavy hydrocarbons are used for extinguishing large magnesium fires. The anti-fire kit operates like safety barrier and finds application in modern fire fighting. Normal safety equipment used by colored glasses should be used when fighting a magnesium fire, for protection of the eyes against the characteristic intense white light.
Source Magnesium . com