Toxic fumes may have overwhelmed two people off-roading at Kaena Point on Saturday.
The suspected case of carbon monoxide poisoning took place on the Mokuleia-side of Kaena State Park. A fisherman found the pair unconscious inside a Jeep Wrangler stuck in a deep mud puddle.
The area is a popular spot for 4x4s. Several of those vehicles, including other Jeeps, made the trip on Kaena Point Road Sunday, a day after the incident.
Authorities said the muffler was submerged, the engine was running and the windows were rolled up.
"If you smell something toxic, you just get away from it," said veteran auto mechanic George Nitta. "But if you don't smell anything, how do you know it's poisonous? You don't. And that's why carbon monoxide is so dangerous."
"The symptoms are gradual so the persons in the vehicle wouldn't notice that they were indeed being poisoned. They would feel sleepy, perhaps a headache, and then go to sleep," explained David Jenkins of the Honolulu Fire Department.
Nitta said even if the exhaust is submerged, a vehicle's engine can keep going. "As long as the intake can take air, it'll keep running because the exhaust, it just pumps out, like a compressor. And if it can't go out one side, it'll go out another."
Nitta believes many vehicles need to have their exhaust systems checked thoroughly. While they may appear to be okay from the bottom in a visual inspection, he suggests having the top inspected for cracks.
Nitta doesn't know the actual vehicle that was involved in the incident. However, "My guess is that with that vehicle that they got carbon monoxide, the exhaust is leaking from the top and shooting it up" into the cabin.
Bystanders performed CPR until emergency crews arrived. The 33-year-old man and 25-year-old woman were listed in critical condition. Authorities believe they were inside the Jeep for at least an hour.
Nitta also has first-hand knowledge about carbon monoxide poisoning. He got it himself when he first got started as a mechanic in the 1960s.
"It took me months to get over it," he said. "It's not like you breathe something bad and walk outside and it's okay."