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ASHRAE Research Project 1614: Determining the Effectiveness of UVC Systems on Commercial Cooking Effluent

ASHRAE Research Project 1614

Determining the Effectiveness of UVC Systems on Commercial Cooking Effluent

From ASHRAE Journal Newsletter, August 11, 2020

Emissions from commercial restaurant cooking can cause health and hygiene risks, a decrease in ventilation system efficiency and fire accidents. Including ultraviolet-C (UVC) lamps with a Type I hood in the ventilation system might reduce the grease deposition on the ductwork and pollution in the exhaust.

A Science and Technology for the Built Environment article about a recently completed ASHRAE research project aimed to provide further design guidance for commercial kitchen ventilation systems by developing a method of testing to evaluate the performance and effectiveness of UVC systems on commercial cooking effluent. Researcher Meng Kong, Ph.D., Associate Member ASHRAE, discusses the project.

1. What is the significance of this research?

Kong: The research provided the community with increased expertise in providing design guidance for commercial kitchen ventilation systems, developed a better understanding on the effectiveness of UVC systems on commercial cooking effluent and established an accurate, effective and economical method of test for the evaluation of the UVC effectiveness. It provided a firm scientific basis toward the next standard building codes and regulations within the foodservice industry.

2. Why is it important to explore this topic now?

Kong: The resulting processes of UVC systems in commercial kitchen hoods may affect the emission airstream by changing particle size distribution, particle reactivity, gas-to-particle partitioning, volatile organic compounds (VOC) compositions and concentrations. The UV treatment could increase or decrease the amounts of fugitive free radicals, ozone, aldehydes, reactive organic gases with high maximum incremental reactivity (MIR), and carcinogenic polycyclic aromatic hydrocarbon (PAH) concentrations. These changes impact indoor air quality (IAQ) and public health and eliminate fire risks and costly cleaning operations.

The lack of solid measurements and understanding of the UVC system effectiveness in commercial cooking effluent can pose some problematic concerns in designing and operating commercial kitchen exhaust systems, especially when there is no proven method of test for this purpose. The above possible benefits of UVC systems are not systematically proven to be effective. If they are proven, many restaurant owners and industrial designers of cooking hoods could enjoy the system benefits, including reduced duct cleaning intervals, decreased likelihood of duct fires, reduction of ventilation energy due to pressure drop decrease along cooling coils, increased heat exchanger efficiencies in commercial kitchen ventilation systems and reductions of VOCs and grease particulate emissions.

Quantitative testing can also make recommendations for the effectiveness of a UVC system and the quantification of its benefits based on the data from elaborate and comprehensive analyses.

3. What lessons, facts, and/or guidance can an engineer working in the field take away from this research?

Kong: From this research, engineers could learn that the design of the kitchen ventilation system is critical in maintaining a clean, safe and healthy environment in commercial restaurants. The application of the UVC system may reduce the exhaust pollution and grease deposition in the exhausting duct only if enough residence time of the exhaust is guaranteed. A better filtration system is also important since it can not only trap the grease and pollutant in the duct but also increase the residence time dramatically.

4. How can this research further the industry's knowledge on this topic?

Kong: The current knowledge of this topic in the industry is still not enough. The use of the UVC system in commercial kitchens needs to be investigated further to better understand the mechanism and potential benefits and risks to the environment, especially the long-term cumulative performance of the UVC system. The UVC system oxidizes the pollutants, but its contribution to the reduction of the emission and grease deposition during cooking was very limited. The whole UVC hood system (i.e., including the primary filter, secondary filter and UVC lamp) was able to reduce the emission and deposition rate significantly. The secondary emission introduced by the UVC reaction also needs to be investigated and evaluated.

5. Were there any surprises or unforeseen challenges for you when preparing this research?

Kong: When we were preparing for this study, because there were very few similar studies done before, we did not realize how much pollution or grease deposition each cooking test would generate. It was difficult determining the necessary cooking amount, selecting an appropriate sampling and measuring device and method (for example the particle counter) and determining the best way to measure the combustion heat, flammability and solubility. We later developed a new approach to collect enough samples for flammability quantification.