in exhaust from the engines of improperly ventilated boats, for example; it can occasionally be introduced into scuba tanks if they are carelessly filled. Symptoms of carbon monoxide poisoning initially include headache, nausea and fatigue and can progress to dizziness, seizures, respiratory arrest and even death. First aid should include the administration of supplemental oxygen. Odor from a breathing gas can indicate a toxic compound. Immediately report any odors, no matter how faint, to a dive professional or the filling station. It is also vital for divers to understand the implications of flying or driving to a high elevation soon after diving. The lower pressure in an aircraft cabin or at altitude may cause decompression illness in previously asymptomatic divers or worsen existing symptoms. Divers without any DCI symptoms can use the following guidelines for surface intervals before flying in an unpressurized aircraft at altitudes of 2,000 to 8,000 feet (610 to 2,438 meters) or in a pressurized aircraft cabin: • A preflight surface interval of at least 12 hours following a single nodecompression-stop dive • A preflight surface interval of at least 18 hours following multiple dives per day or multiple days of diving • A preflight surface interval of at least 24 hours following dives that require decompression stops These suggested preflight surface intervals do not guarantee that a diver will avoid DCI, but longer surface intervals will further reduce the risk.
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