A study conducted by the National Institute for Occupational Safety and Health found that uncontrolled generators routinely emit carbon monoxide concentrations well above NIOSH’s immediately-dangerous-to-life-or-health value of 1,200 parts per million.

 “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,” Capt. Ronald M. Hall, deputy branch chief in the Engineering and Physical Hazards Branch in the NIOSH Division of Applied Research and Technology, said in a statement. “These hazardous conditions were exacerbated when the drive engines were operating, placing employees who worked on or around the boats, as well as the boat operators, at risk.”

After the investigations, NIOSH engineers worked with major houseboat and generator manufacturers to develop novel engineering controls to reduce carbon monoxide exposure and poisonings.

Between 2004 and 2005, the two largest manufacturers of marine generators introduced low carbon monoxide emission models, which resulted in reductions of as much as 99 percent in carbon monoxide concentrations in occupied areas on and around the boats.

In addition, NIOSH worked with the Environmental Protection Agency to put regulations in place that affect marine engines. The new regulations, which apply to carbon monoxide emissions from generators, sterndrive and inboard engines and personal watercraft and outboard engines, are expected to result in significant reductions in carbon monoxide emissions.