Utah State Parks Blog

Carbon Monoxide – The Silent Killer

SALT LAKE CITY — Known as the silent killer, Carbon Monoxide is odorless and tasteless. High levels of inhalation can result in death.

Carbon Monoxide (CO) is produced from the burnt emissions of a fuel ignited motor and is emitted from the exhaust ports of the motorized engine of a boat. CO can build up, depleting oxygen to the point of death.

A person who is sleeping or intoxicated can die from CO poisoning before ever having experienced symptoms. CO poisoning can also cause a person to pass out, fall into the water, and drown.

CO can build up in boats from:

  • Back drafting– It 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 the exhaust.
  • Traveling at slow speeds or idling– Slow speeds or idling 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.
  • Generators– On large houseboats, generators oftentimes vent to the rear of the boat where there is a swim deck or 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.
  • Other vessels-Exhaust from another vessel that is docked, beached, or anchored alongside your boat can emit CO into the cabin and cockpit of your boat. Even with properly vented exhaust, your boat should be a minimum of 20 feet from the nearest boat that is running a generator or engine.
  • Blockage of exhaust outlets– Blockage can cause carbon monoxide to accumulate in the cabin and cockpit area – even when hatches, windows, portholes, and doors are closed.


Early symptoms of poisoning include headache and nausea. If a passenger is experiencing these symptoms, immediately move the person to fresh air, investigate the cause and take corrective action.

Don’t confuse these symptoms with seasickness or intoxication. Seek medical attention, if necessary.

Be aware of carbon monoxide poisoning symptoms. These include headache, dizziness, weakness, nausea, vomiting, chest pain, and confusion.

Be aware of what you can do to prevent CO poisoning. Install and maintain a working CO detector listed as appropriate for marine use inside the boat to alert people when dangerous levels of CO have built up inside the boat cabin.

Some quick tips to help avoid the dangers of CO are:

  • Properly install and maintain all fuel-burning engines and appliances.
  • Educate all passengers about the signs and symptoms of CO poisoning.
  • Swim and play away from areas where engines vent their exhaust.
  • Watch children closely when they play on rear swim decks or water platforms.
  • Never block exhaust outlets (Blocking outlets can cause CO to build up in the cabin and cockpit areas–even when hatches, windows, portholes, and doors are closed).
  • Dock, beach, or anchor at least 20 feet away from the nearest boat that is running a generator or engine. Exhaust from a nearby vessel can send CO into the cabin and cockpit of a boat.
  • If your boat is stopped in the water, never have the engine running.

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