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An evaluation of vertical exhaust stacks and aged production emission control devices to prevent carbon monoxide poisonings from houseboat generator exhaust.

Earnest GS; Hall RM; Dunn KH; Hammond D; Valladares R
Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, EPHB 171-32a, 2003 Oct; :1-45
Working under an interagency agreement with the United States Coast Guard, researchers from the National Institute for Occupational Safety and Health (NIOSH) evaluated carbon monoxide (CO) emissions, exposures, and controls from gasoline-powered generators on houseboats at Fun Country Marine Industries. This evaluation is part of a series of studies conducted by NIOSH investigators during the past several years to identify and recommend effective engineering controls to reduce the CO hazard and eliminate CO poisonings on houseboats and other recreational marine vessels. Performance of a 9-foot, vertical exhaust stack on three rafted houseboats and the performance of several production emission control devices (ECDs) with several thousand operating hours manufactured by Enviromarine LLC were studied. The vertical exhaust stack has been retrofitted onto over 90% of the gasoline-powered generators used on the Forever Resort's houseboat rental fleet at Callville Bay Marina on Lake Mead near Henderson, Nevada. The vertical exhaust stacks used on Forever Resort's houseboats were constructed from continuous aluminum pipes that extended 9-feet above the houseboats' upper decks. The exhaust stacks were designed to comply with the recently revised American Boat and Yacht Council (ABYC) Standard P-1 for recreational boat exhaust. The remaining Forever Resort's houseboat generators were retrofitted with Enviromarine LLC ECDs in order to address the carbon monoxide CO problem. Production ECDs were retrofitted onto gasoline-powered houseboat generators to reduce the CO concentrations in the generator exhaust and prevent poisonings. In June 2001, NIOSH researchers evaluated a recently developed marine prototype ECD, and the performance was excellent (CO concentrations on the houseboat's lower stern deck were below 1 ppm, and CO concentrations were reduced by approximately 99%). In October 2001, the same ECD was reevaluated after it had been used on the houseboat's generator and exposed to lake water and other natural elements for approximately 3,000 hours of operation. During this evaluation, the prototype ECD's performance was found to have substantially degraded due, in part, to internal corrosion from exposure to water and other elements. The current study evaluated several redesigned production ECDs with an outer shell casing made entirely of stainless steel. The production model ECD was designed to withstand the harsh marine environment. The ECDs evaluated during the current survey had over 2,000 operating hours. During this study, the vertical exhaust stacks performed well, and the results were consistent with the results of previous NIOSH investigations. When the houseboats were rafted together and stationary, average CO concentrations measured, at all locations on the houseboats, were well below 5 ppm. Results from the aged production ECD evaluations showed that they were somewhat effective at reducing CO concentrations; however, their performance had substantially degraded from when they were new. CO concentrations exhausting from the 2 generators with ECDs were potentially hazardous (CO concentrations exceeding 500 ppm were measured on the lower rear deck of one boat). This degradation in ECD performance is believed to be related to lack of adequate maintenance on the generators. Based upon the results of this and previous studies, NIOSH investigators recommend that houseboats using gasoline-powered generators, should be evaluated for potential CO exposures and poisonings near the lower stem deck. Houseboat owners should consider retrofitting the generators with engineering controls to reduce the potential hazard of CO poisoning and death to individuals on or near the houseboat. The vertical exhaust stack has performed well during all previous NIOSH evaluations and is successfully being used on many houseboats across the U.S. The ECD continues to be a promising emission control option; however, generator maintenance is critical to ensure that the ECD performs properly and does not present a potential CO or fire hazard. In many cases, installation of a high temperature shutoff switch should also help to prevent this problem. Because performance complications were noted during this and a previous NIOSH field evaluation, additional testing and evaluation of the ECD is warranted. Finally, other engineering control options such as fuel injected generators and other catalysts are being developed. These options could also play an important role in the future in reducing CO emissions and poisonings from marine generators and engines.
Poison-control; Poison-gases; Boat-manufacturing-industry; Engineering-controls; Gas-sampling; Emission-sources; Environmental-control-equipment; Environmental-exposure; Equipment-design; Equipment-reliability; Exhaust-gases; Exposure-levels; Exposure-limits; Control-technology; Region-9; Marine-workers
National Institute for Occupational Safety and Health, Division of Applied Research and Technology, 4676 Columbia Parkway, MS-R5 Cincinnati, OH 45226
Publication Date
Document Type
Field Studies; Control Technology
Funding Type
Interagency Agreement
Fiscal Year
NTIS Accession No.
NTIS Price
Identifying No.
NIOSH Division
Priority Area
Research Tools and Approaches: Control Technology and Personal Protective Equipment
Source Name
National Institute for Occupational Safety and Health
Page last reviewed: June 15, 2021
Content source: National Institute for Occupational Safety and Health Education and Information Division