Health hazard evaluation report, HETA 2003-0318-2936, evaluation of two exhaust stack configurations on two houseboats at Table Rock Lake, Missouri.
In response to a request from the Houseboat Industry Association (HIA) and working under an interagency agreement with the United States Coast Guard, the National Institute for Occupational Safety and Health (NIOSH) evaluated carbon monoxide (CO) exposures and engineering controls associated with gasoline-powered generator exhaust on houseboats. The current health hazard evaluation (HHE) is part of a series of studies conducted by NIOSH investigators to identify and recommend effective engineering controls to prevent CO poisonings on houseboats and other recreational marine vessels. In the Spring of 2003, the HIA sent a letter to NIOSH and the Coast Guard Office of Boating Safety requesting further testing of houseboats having generator exhaust stacks. HIA indicated that their members would provide houseboats and testing sites. HIA members were concerned that previous NIOSH evaluations of houseboat generator exhaust stacks failed to include all appropriate environmental and operational conditions. Therefore the HIA requested that additional testing be performed under the following conditions: 1) in a cove, 2) after dark, 3) under various generator loads, 4) at different houseboat trim angles, and 5) during temperature inversions. Side exhaust versus stack exhaust was also evaluated. NIOSH researchers conducted two field evaluations in August 2003. The evaluation at Lake Cumberland, Kentucky, was described in a separate report (NIOSH Publication No. EPHB 171-34a). The evaluation at Table Rock Lake, Missouri is described in this report. The houseboats evaluated at Table Rock Lake were provided by Fun Country Marine Industries and Sumerset Houseboats. The evaluation at Lake Cumberland found problems with the stack design where CO gases were discharged with the water on the side of the boat. Based on those results, design changes were made to help alleviate the problem on houseboat #2 at Table Rock Lake. The design changes included the removal of a 3 foot (2 inch inner diameter) section of flexible exhaust hose, and the removal of a 180 degree angle. This survey indicated that high temperature/high humidity environments, generator loading, and houseboat trim angles had relatively small effects on exhaust stack performance. Results of this study were consistent with those of previous NIOSH exhaust stack evaluations. Both exhaust stacks on the two houseboats performed dramatically better than side exhaust (even on the upper deck of the houseboat). With the exhaust stack, results indicated a reduction of mean and peak CO concentrations of approximately 87% to 99.9%, when compared to results obtained with the side exhaust, at the majority of outside lower deck locations on both houseboats. On the upper deck of the houseboats, mean and peak results obtained with the exhaust stack indicated a range of reductions of approximately 47% to 99% in the majority of upper deck locations, when compared to the side exhaust configuration. Based upon the results of NIOSH exhaust stack studies, investigators recommend that houseboats using gasoline-powered generators be evaluated for potential CO exposures and poisonings, especially near the lower stern deck. Houseboat manufacturers, rental companies, and owners should consider retrofitting their gasoline-powered generators with engineering controls to reduce the potential hazard of CO poisoning and death. Other engineering control options such as cleaner burning engines and after-treatment devices are being developed, and these options could also play an important role in preventing future poisonings Properly installed exhaust stacks have performed well during all NIOSH evaluations, and they are successfully being used to help prevent CO poisonings on hundreds of houseboats across the U.S. During this evaluation, the exhaust stacks performed well under a variety of environmental and operational conditions. Keywords: (Establishments primarily engaged in operating marinas and which perform incidental boat repair) carbon monoxide, houseboats, boats, exhaust stack, side exhaust