Larger boats, such as houseboats, sometimes have generators that vent toward the rear of the boat. This venting poses a danger of CO poisoning to people on the rear swim deck or water platform. On larger boats CO builds up above the water near the water platform. CO that builds up in the air space beneath the stern deck or on and near the swim deck can kill someone in seconds.
Traveling at slow speeds or idling in the water can cause CO to build up in a boat’s cabin, cockpit, bridge, and aft deck, or in an open area. Wind from the aft section of the boat can increase this buildup of CO.
Back drafting can cause CO to build up inside the cabin, cockpit, and bridge when a boat is operated at a high bow angle, is improperly or heavily loaded, or has an opening that draws in exhaust.