Lawrence Berkeley National Laboratory

Burners and cooking activities are both major sources of air pollutants in many residences. Mechanical kitchen ventilation can effectively reduce cooking-related indoor air pollution but the knowledge about kitchen ventilation device performance and usage in real homes remains limited. We reviewed recent lab, field and survey studies that investigated the performance and occupant use patterns for mechanical kitchen ventilation devices. We have found the following three major issues. Firstly, in-home performance is lower than what was certificated in laboratory testing. In several recent field studies, researchers investigated 125 US single family homes and 23 apartments and found 82 homes had range hoods or over-the-range microwaves (OTR) certificated by Home Ventilating Institute (HVI) that had working airflows greater than 100 cfm. However, the field measurements showed only 44 of them had installed airflow that matched the rated, with the average ratio of installed versus rated flow of 0.76. The lower installed airflows were due to high air flow resistance of duct venting systems, incorrect installation and dirty hood inlets. Second, the knowledge of range hood performance for pollutant removal before mixing into the room (i.e. capture efficiency) is very limited. We found the capture efficiency was only measured for 57 hoods in 9 studies in the US, either in the lab or in the field. The measured capture efficiency ranged from 10% to 100%, generally increasing with the airflows. The capture efficiency can be influenced by the burner location, hood airflow, range hood geometry and test conditions. The main reason for limited capture efficiency data was the difficulty in conducting field measurements. Third was that the actual usage of the kitchen ventilation during cooking is low. Occupants often do not use their range hood due to the lack of awareness of the benefits of kitchen ventilation. A large survey study in Canadian homes showed that 30% of households reported regularly using their range hood. After being informed of the benefits of kitchen ventilation, the overall willingness to use the range hood was significantly higher. Field data from California showed range hoods were only used for 36% of cooking events in houses and 28% in apartments, though the occupants claimed they used them more frequently.