Any failure of cabin pressurization above requires an emergency descent to or the closest to that while maintaining the Minimum Sector Altitude (MSA), and the deployment of an oxygen mask for each seat. The oxygen systems have sufficient oxygen for all on board and give the pilots adequate time to descend to below . Without emergency oxygen, hypoxia may lead to loss of consciousness and a subsequent loss of control of the aircraft. Modern airliners include a pressurized pure oxygen tank in the cockpit, giving the pilots more time to bring the aircraft to a safe altitude. The time of useful consciousness varies according to altitude. As the pressure falls the cabin air temperature may also plummet to the ambient outside temperature with a danger of hypothermia or frostbite.