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Characterization of cooking effluent from seven commercial kitchen appliances and representative food products.

Article Excerpt
INTRODUCTION

Characterization of emissions from cooking processes continues to be of interest, with an emphasis on grease accumulation on surfaces in kitchens and within exhaust systems and its impact on cleaning and fire potential. Indoor airborne emissions may create potential health hazards to cook staff and others within the building; widespread dissemination to outdoors will impact atmospheric chemistry and air quality.

Several regulations on emissions from commercial kitchens have been adopted in the U.S. The South Coast Air Quality Management District (SCAQMD 1997) implemented Rule 1138 that requires emission controls on certain chain-driven charbroilers within the district. More recently, the Bay Area Air Quality Management District (BAAQMD 2007) adopted Rule 2 of Regulation 6 that also requires emission controls on chain-driven charbroilers beginning January 1, 2009. In addition, control of underfired charbroiler emissions is scheduled to be phased in between January 1, 2010, and January 1, 2013.

An annotated bibliography was written (Gerstler et al. 1996) that includes 74 references on measured cooking effluent and technologies related to its sampling and analysis. Since the review's publication, several additional studies were reported that add to the archival literature.

Residential applications have been the focus of some research. A series of papers document a study conducted by the National Exposure Research Laboratory in Reston, Virginia. The first paper (Wallace 2000) documented several sources of particles and evaluated the levels of polycyclic aromatic hydrocarbons (PAH) and carbon monoxide in a townhouse with no external ventilation from the kitchen. Cooking was found to be the major source of particles in the building. The levels of PAH were deemed insignificant, so they were not monitored in future work at the site. A subsequent paper (Wallace et al. 2004) focused on particles from 10 nm to 2.5 [micro]m in size. Forty-four cooking episodes were selected for analysis, as it was determined that cooking (mostly frying in a skillet) was capable of producing more than ten times the ultrafine particle number emissions than other activities. Typical cooking episodes produced particles at a rate of about [10.sup.14] particles/h during a 5-15 min cooking cycle. Ultrafine (<100 nm) and accumulation mode (0.1-1 [micro]m) particle sources were analyzed for various activities. The highest mean number concentrations were produced by what was termed "complex cooking" on a gas stove that generated between 35,000 and 50,000 [cm.sup.-3] compared to less than 1% of this when no indoor sources were observed. A related study was performed using personal exposure monitors on 37 participants in their own homes. The highest mean source strengths were identified from burned food (470 mg/min), grilling (173 mg/min), and using a fry pan (60 mg/min). A group at the University of Aberdeen Medical School in Aberdeen, Scotland (Dennekamp et al. 2001), performed a study in which emissions from both electric and gas-operated cooking appliances were conducted in a small (70 [m.sup.3]) unventilated chamber that simulated a small residence. Particles from 10 to 500 nm NO and [NO.sub.2] were analyzed. Conclusions drawn from this study were that potentially toxic concentrations of small particles and very high concentrations of oxides of nitrogen can be generated without adequate exhaust ventilation.

Effluents from commercial cooking processes were also investigated. Particulate (Kleeman et al. 1999) and organic compounds (Schauer et al. 1999) emitted from meat charbroiling were measured at a commercial kitchen field site. Samples were obtained in the exhaust duct downstream of the grease filters installed in the exhaust hood. Frozen and thawed hamburger patties (20% fat) were cooked on a natural gas-fired charbroiler. Total mass emission rates were determined to be approximately 30 g/kg meat cooked. Peak particle mass concentration was determined using a micro-orifice uniform deposit impactor (MOUDI) and was found to be near 0.2 [micro]m. Although inorganic composition was investigated, the vast majority of the effluent consisted of organic compounds. Several nonmethane volatile organic compounds and semi-volatile organic compounds were identified including n-alkanoic acids, n-alkenoic acids, and carbonyls.

Personal exposure of the cook staff in 19 commercial kitchens was made in Norway (Svendsen et al. 2002) using glass fiber filter cassettes and a sampling device for aldehydes. Results showed that in some types of kitchens the concentration of fat aerosols can reach 6.6 mg/[m.sup.3], and the sum of aldehydes can attain 185 [micro]g/[m.sup.3]. Exposures were found to be greater in small kitchens than in chain restaurants or hotel kitchens.

A more recent series of measurements conducted at the University of California Riverside CE-CERT facility was reported (McDonald et al. 2003). Emissions from several appliances were measured, all in the exhaust duct, after which they were sent through a dilution tunnel and then a residence chamber to approximate the conditions expected after release to the ambient. Particulate mass emission factors were considerably less than measured in earlier studies and ranged from 4.5 g/kg for 21% fat hamburger cooked on a chain-driven char-broiler to 15 g/kg for 25% fat hamburger cooked on an under-fired charbroiler. The majority of the mass was determined to be organic carbon with significant amounts of PAHs (primarily naphthalene), lactones, and cholesterol.

Cooking exhaust from 15 commercial kitchens was sampled and analyzed for 13 carbonyl compounds in Hong Kong (Ho et al. 2006). Various restaurant types were included in the survey that represented different cooking processes and food styles. The authors concluded that, on a total mass emissions basis, the top four carbonyls (formaldehyde, acetaldehyde, acrolein and nonanal) contribute 72% of the carbonyl emissions from commercial kitchens in Hong Kong.

The main goal of this investigation is to extend the data on particulate and condensable vapor emissions from commonly used commercial kitchen appliances and food products that were previously documented in the ASHRAE RP-745 final report dated February 9, 1999 (Gerstler et al. 1999a). As with the previous study, appropriate food products were selected for each appliance to provide significant grease emissions and to be in accordance with corresponding ASTM International test protocol requirements. Table 1 provides the seven appliances that were tested and the food product used for each.

The main particle sampling instrument, the personal cascade impactor, and the same grease vapor sampling instrument, the EPA Method 5 sampling train, were used in this study so the results could be compared directly with the results obtained in ASHRAE RP-745. Data were obtained both in the plume from each appliance, as in the earlier study, and also in the exhaust duct with no grease filters installed in the hood.

One of the observations from the earlier study was that a significant fraction of the particulate mass...

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