Since the Vietnam War and the 1967 USS Forrestal fire, United States Navy and United States Marine Corps GP bombs are distinguished by a thick ablative fire-retardant coating, which is designed to delay any potential accidental explosion in the event of a shipboard fire. Land-based air forces typically do not use such coatings, largely because they add some 30 lb (14 kg) to the weight of the complete weapon. Fire is less a danger in a land-based facility, where the personnel can be evacuated with relative ease, and the building be the only loss. At sea, the crew and munitions share a facility (the ship), and thus are in much more danger of fire reaching munitions (which tend to be more closely packed, due to space limitations). Also, losing a munitions storage building on land is far cheaper than sacrificing an entire naval vessel, even if one could easily evacuate the crew.