A new study simulating carbon monoxide levels in detached and manufactured homes commissioned by the U.S. Consumer Product Safety Commission shows that that operating a generator for 18 hours is likely to result in high CO exposures whether the generator is in the house or the garage; and that generators that have been modified to limit CO emissions using a shut-off mechanism or other technology can significantly reduce exposure compared to generators without emissions controls.

Last September, our blog Home Use Generators: Dangerous and Behind the Curve documented the rising incidence rate of CO poisonings linked to the use of home generators as extreme weather events and an aging power grid result in more and more prolonged outages. The agency’s response has been to closely track the data and promulgate a stronger warnings rule. Heightened hazard language has done little to dissuade homeowners from putting portable generators in locations that can create significant health risks for home occupants.

The simulation study authors noted that CPSC has recorded 755 deaths from CO poisoning associated with home generators, from 1999 through 2011, with nearly three-quarters of those occurring between 2005 and 2011, and many of which occurred during power outages.

In late October 2011, Connecticut was hit by a rare early-season snowstorm that left more than 860,000 businesses and homes in that state without power. And some state residents who didn’t or couldn’t wait for the power to be restored, tried to survive the outage with the use of a portable generator. From the day of the storm until November 9, the Department of Public Health received 143 reports of carbon monoxide poisoning – nearly nine times the number of reports – 16 – for the previous three years combined. Five individuals died and 41 required a hospitalization; the majority of incidents were caused by portable generators for home use.

In writing about this surge in the Connecticut Epidemiologist, the researchers noted: “Outbreaks of CO poisonings following winter storms are well documented and continue to be a problem.”

Carbon monoxide (CO) is a potentially deadly gas found as a byproduct of internal combustion engines that is odorless, colorless and tasteless. According to the latest figures from the CPSC, from 1999 to 2011, 695 – nearly 80 percent – of the 881 fatalities from 513 incidents were associated with generators. And CO poisonings from home generators will continue to be a problem, because the only countermeasure mandated by the U.S. Consumer Product Safety Commission are warnings. While other engine-manufacturing industries, such as automotive and marine generators, use available technology to significantly reduce their CO emissions, makers of portable generators for home have been relying on capital letters and pictograms to avert injury and death.

The data suggest that dramatically worded warning labels don't do enough to depress the injury and mortality rate. According to CPSC spokesman Scott Wolfson, there was a noticeable decline in CO incidents involving generators after the recent Mid-Atlantic derecho and Hurricane Issac. Nonetheless, the CPSC has been exploring technical solutions to the CO hazard since 2006.