Ventilation Guidance for Residential Kitchen with Gas Stove
We performed systematic analyses using a simple mass balance approach and Computational Fluid Dynamics (CFD) simulations to evaluate the impact of several parameters on the concertation levels of Nitrogen dioxide (NO2) and resulting occupant exposure. This first blog presents the mass balance results and guides in operating the kitchen exhaust based on these results. A separate blog is developed to explain the CFD analysis results.
Analysis with the Mass Balance Approach
The mass balance approach considers the kitchen space as a large well-mixed control volume without consideration for the spatial variations in the contaminant concentration within the space. It predicts the transient variation of the “volume-averaged” contaminant concentration by balancing the rate of contaminant generation with the rate of contaminant removal by the ventilation air. The parameters evaluated were the exhaust air flow rate, delay in starting the exhaust fan after starting the burner, the duration for which the exhaust fan is left running after the burner is turned off, and the size of a kitchen.
Guidance for Operating the Kitchen Exhaust Fan
Based on the above mass balance analyses the following guidelines are developed:
- Kitchens should operate with an exhaust fan flow rate of at least 100 cfm.
- The exhaust fan should be started within ten minutes of starting the burners (cooking).
- The exhaust fan should be kept on running for at least five minutes after the cooking.
These analyses further indicate that homes with open floor plans (larger kitchens) would experience relatively lower exposure than the small enclosed kitchens. In general, the occupant exposure levels within the first few minutes of cooking remain below the acceptable level.
The limitations of this study are that the mass balance approach assumes instantly well-mixed conditions and cannot predict the spatial variations of pollutants within the space. To predict the concentration in the breathing zone of occupants a detailed three-dimensional transient Computational Fluid Dynamics (CFD) analysis is required.