If you have a gas oven in your kitchen, your cooker hood may not be venting away air pollutants from your gas burners as efficiently as you might think. A new study in the US has revealed that cooking exhaust hoods designed for domestic kitchens vary widely in their ability to capture and vent away pollutants. The study, led by two Lawrence Berkeley National Laboratory scientists, found that of seven models tested, the capture efficiency varied from less than 15 percent to more than 98 percent. The study, by Woody Delp and Brett Singer of Berkeley Labs Environmental Energy Technologies Division, measured pollutant capture efficiency, sound level and airflow. Cooking exhaust hoods vent pollutants such as carbon monoxide, nitrogen oxides, formaldehyde and fine particulates generated during cooking. While the exhaust hoods they tested varied widely in performance, they found that hoods were more efficient at capturing pollutants generated by the two back burners of a four-burner stove than its front burners. Even a moderately effective exhaust hood can reduce a stove users exposure to pollutants, says Delp, and using the back burners preferentially over the front burners helps reduce exposure even more. However, their research suggests that design improvements can increase the ability of hoods to capture pollutants and reduce their noisiness without increasing energy use. Energy ratings for kitchen hoods only consider a hoods energy use and noise level, not its efficiency.