Despite warnings to the contrary, many people continue to operate portable generators indoors or close to open windows, doors or vents, resulting in more than 500 deaths since 2005. And each year, more than 20,000 people visit the emergency room and more than 4,000 are hospitalized due to exposure to toxic levels of carbon monoxide. Fatality is highest among people 65 and older.
A new computer modeling study by NIST researchers scrutinizes the deadly relationship between carbon monoxide emissions and occupant exposure. They conducted simulations of 87 types of dwellings representative of the U.S. housing stock with a generator operating within a room in the house, its basement or attached garage.
The study considered two scenarios of portable-generator operation: continuous operation for 18 hours and operation with some type of control technology that causes the generator to shut off periodically, or so-called "burst" releases.
Regardless of housing type or location, generators that release as little as 27 grams of carbon monoxide per hour continuously for 18 hours cause 80% of the modeled cases to result in an exposure predicted to reach dangerous levels. In comparison, current commercially available generators that were tested by NIST in a previous study emitted CO at a rate of 500 to 4,000 grams per hour.
For generators characterized by burst releases of carbon monoxide, the NIST team found that carbon monoxide emissions of more than 139 grams resulted in dangerous levels of exposure.
The findings, reported to the U.S. Consumer Product Safety Commission, could help in setting limits on carbon monoxide emissions from portable generators.