Current government standards allow for a lower margin of safety against carbon monoxide poisoning in manufactured or mobile homes than in traditional site-built homes, according to a new report from the Government Accountability Office (GAO).
The problem, says the GAO in its report to Congress, is that the Department of Housing and Urban Development (HUD) regulations for ventilation standards in homes has not been updated since 2005 and fails to reflect more effective standards currently used by the home building industry.
For example, HUD's current standards require that homes' air intakes and exhaust vents be separated by a minimum of 3-feet, while building industry standards for site-built homes have required a minimum 15- to 30-foot separation for several years.
Greater separation between exhaust vents and air intakes helps prevent airborne contaminants like carbon monoxide, pollen, dust and pet dander from re-entering the home.
Expert on indoor air quality interviewed by the GAO agreed that the exhaust from an improperly working furnace along with unique wind conditions can, in rare cases, cause carbon monoxide to re-enter the home through air intakes.
GAO's analysis of the experts' input showed that increasing the separation between the exhaust vents and air intakes of manufactured homes - similar to building industry standards for site-built homes - can "significantly dilute concentrations of contaminants" even if they do re-enter the home.
According to 2009 American Housing Survey data, about 5.5 million occupied manufactured homes were built under the HUD Code. While HUD keeps copies of approved plans for manufactured homes, the agency does not maintain data on the actual distances between the air intakes and exhaust vents of each home, and no post-construction testing of air flow performance is required.
What GAO Recommended: Stopping short of recommending that the HUD Code be amended to reflect building industry standards, the GAO recommended that HUD develop and require tests to validate the performance of ventilation systems as part of its certification of manufactured homes.