A new study found houseboats that use gasoline-powered generators without emission controls emit dangerous levels of carbon monoxide, posing a risk to life and health of boaters and marina workers. However, it concludes that effective emission controls, as fitted on many houseboats, can reduce carbon monoxide emissions to well within safe levels.

A report on the study is published in the Journal of Occupational and Environmental Hygiene (JOEH).

As well as outlining the hazards posed by carbon monoxide (CO) levels on houseboats that use uncontrolled generators, it also describes the various controls that are available to reduce exposure.

CO is a poisonous gas – often referred to as the “silent killer” because we cannot see, smell or taste it, and because the dizziness and nausea it causes when we inhale it are often mistaken for other health conditions.

In the study, researchers at the National Institute for Occupational Safety and Health (NIOSH), along with colleagues from the Centers for Disease Control and Prevention (CDC), found that uncontrolled generators on houseboats routinely emit CO concentrations well above the 1,200 parts per million level that NIOSH defines as immediately dangerous to life or health (IDLH).

Captain Ronald M. Hall, first author and deputy branch chief in the Engineering and Physical Hazards Branch in the Division of Applied Research and Technology at NIOSH in Cincinnati, Ohio, says:

Houseboats that exhaust uncontrolled generator combustion gases beneath or near the rear deck indicated that extremely hazardous carbon monoxide concentrations can accumulate in that area.”

He explains how they found the hazardous conditions were made worse when the drive engines were operating, “placing employees who worked on or around the boats, as well as the boat operators, at risk.”

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Researchers have identified more than 800 CO poisonings related to recreational boating in the US.

The team first began investigating CO emissions on houseboats in 2001, to evaluate the health hazards posed by CO emissions from houseboats following reports of such poisonings on and around houseboats.

While CO poisoning associated with indoor exposure has long been recognized, it is not always recognized that severe CO poisoning can also occur outdoors – although such incidents are much rarer, according to the CDC.

Epidemiological studies have shown that between 1990 and 2008, there were 309 houseboat-related CO poisonings in the US – 26 of which resulted in death. The majority of these poisonings were directly attributable to generator exhaust.

The authors also note: “More than 800 CO poisonings related to recreational boating in the US have been identified, and that number continues to increase.”

They employed a range of sampling methods to analyze CO emissions, including emission analyzers, direct-reading monitors, detector tubes and gas chromatography using evacuated containers.

Following the investigations, NIOSH engineers began working with houseboat and generator manufacturers to develop ways to control CO emissions and reduce exposure and subsequent poisonings.

By 2005, the two largest manufacturers of marine generators had introduced low carbon monoxide emission models.

At the same time, NIOSH and the Environmental Protection Agency put in place regulations for CO emissions from marine engines, including generators, stern-drive and inboard engines, and personal watercraft and outboard engines. These are expected to result in further reductions of CO emissions.

The study reports that air samples from houseboats that were equipped with engineering controls to reduce CO exposure showed they were highly effective and reduced CO levels by over 98% in occupied areas on and around the boats.

The investigators conclude that:

The engineering control devices used to reduce the hazardous CO emissions from gasoline-powered generators on houseboats were extremely effective at reducing CO concentrations to safe levels in potentially occupied areas on the houseboats and are now beginning to be widely used.”

In April 2014, Medical News Today reported how a US study showed snowstorms and power outages increase risk of CO poisoning. Researchers found the majority of CO exposures occurred during the first day following snowstorms and the second and third days following power loss storms.