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Modeling the Effects of Outdoor Gasoline Powered Generator Use on Indoor Carbon Monoxide Exposures



Wang Liangzhu, Steven Emmerich


The U.S. Centers for Disease Control and Prevention (CDC) has reported that up to half of non-fatal CO poisoning incidents during the hurricane seasons in 2004 and 2005 involved generators operated outdoors but within seven feet of the home. The guidance provided on the safe operating distance of a generator is often neither specific nor consistent. Furthermore, some generator manufacturers recommend the use of extension cords to be "as short as possible, preferably less than 15 feet long, to prevent voltage drop and possible overheating of wires". However, the use of short extension cords may result in placement of the generator too close to avoid the home to reduce the likelihood of the entry of CO. This study modeled multiple scenarios of a portable generator operated outdoors using the CONTAM indoor air quality model coupled with a computational fluid dynamics (CFD) model to predict CO concentrations near and within a home. The simulation cases included both human-controllable factors (e.g., generator location and exhaust direction and window opening size) and non-controllable factors (e.g., wind, temperature, and house dimensions). For the house modeled in this study, a generator positioned 4.6 m (15 feet) away from open windows may not be far enough away to limit CO entry into the house. It was also found that winds perpendicular to the open window resulted in more CO infiltration than winds at an angle, and lower wind speed generally led to more CO entry. To reduce CO entry, the generator should ideally be positioned outside of airflow recirculation region near the open windows.
Technical Note (NIST TN) - 1637
Report Number


Generator, carbon monoxide, generator safe operating distance, CONTAM, computational fluid dynamics, indoor air quality, health, multizone airflow model, poisoning, simulation


Liangzhu, W. and Emmerich, S. (2009), Modeling the Effects of Outdoor Gasoline Powered Generator Use on Indoor Carbon Monoxide Exposures, Technical Note (NIST TN), National Institute of Standards and Technology, Gaithersburg, MD, [online],, (Accessed April 16, 2024)
Created August 2, 2009, Updated October 12, 2021