KwangHoon Han

Determination of material emission signatures by PTR-MS and their correlations with odor assessments by human subjects

UNLABELLED The objectives of this study were to determine volatile organic compound (VOC) emission signatures of nine typical building materials by using proton transfer reaction-mass spectrometry (PTR-MS) and to explore the correlation between the PTR-MS measurements and the measurements of acceptability by human subjects. VOC emissions from each material were measured in a 50-l small-scale chamber. Chamber air was sampled by PTR-MS to determine emission signatures. Sorbent tube sampling and TD-GC/MS analysis were also performed to identify the major VOCs emitted and to compare the resulting data with the PTR-MS emission signatures. The data on the acceptability of air quality assessed by human subjects were obtained from a previous experimental study in which the emissions from the same batch of materials were determined under the same area-specific ventilation rates as in the case of the measurements with PTR-MS. Results show that PTR-MS can be an effective tool for establishing VOC emission signatures of material types and that there were reasonable correlations between the PTR-MS measurements and the acceptability of air quality for the nine materials tested when the sum of selected major individual VOC odor indices was used to represent the emission level measured by PTR-MS. PRACTICAL IMPLICATIONS The study shows that unique emission patterns may exist for different types of building materials. These patterns, or signatures, can be established by using PTR-MS, an online monitoring device. The sum of selected major individual VOC odor indices determined by PTR-MS correlates well with the acceptability of air quality assessed by human subjects, and hence provides a feasible approach to assessing perceived indoor air quality. This online assessment will open a new gate in understanding the role of VOC emissions from building materials on perceived air quality, forming a good foundation to develop real-time or near real-time methods for standard material emission testing and labeling, quality control of emissions from materials, and assessing the acceptability of air quality in buildings.

Evaluation of filter media performance: Correlation between high and low challenge concentration tests for toluene and formaldehyde (ASHRAE RP-1557)

To guide the selection of gas phase filtration media in the air cleaning devices, it is important to understand and estimate the media performance under usage concentrations. Filters for improving indoor air quality are typically subject to low volatile organic compounds (VOCs) concentration levels (e.g., ∼50 ppb), while the current standard tests per ASHRAE 145.1 (ANSI/ASHRAE 2008). are performed at relatively high challenge concentrations (∼1–100 ppm level). The primary objective of this study was to determine if media that perform well at the high concentration test condition would also perform well under the low concentration. The secondary objective was to investigate if and how existing models of filtration by media bed can be applied to extrapolate the results from the high concentration tests to the low concentration condition. Experiments and simulations were carried out at both high concentrations (100 ppm for toluene and 1 ppm for formaldehyde) and low concentrations (0.05 ppm for toluene and formaldehyde) for six selected filtration media. The results show that (1) the high concentration test data were able to differentiate the relative performance among the media at the low concentration properly, confirming the validity of using ASHRAE 145.1 (ANSI/ASHRAE 2008) for relative performance comparison; (2) significant initial breakthrough observed at high concentration tests of large pellet media was not present at the low concentration tests, indicating the dependency of the adsorption capability of the sorbent media on the concentration level as well as the possible “by-pass” effects (i.e., not all the VOC molecules in the air stream had the same chance to contact with the sorbent media); and (3) existing models need to be improved by incorporating the concentration dependency of the partition coefficient and the by-pass effect in order to predict the breakthrough curve at low concentrations properly. Such an improved model was proposed, evaluated with the measured data, and was found to be promising for physical sorbent, but requires further development for chemical, catalytic sorbent and large pellet sorbent. The study provides previously unavailable experimental data and new insight into the behavior of the filtration media for volatile organic compounds as well as evidence in support of the application of ASHRAE Standard 145.1 (ANSI/ASHRAE 2008) for media performance evaluation.

Measurements of grease emission and heat generation rates of electric countertop appliances (RP-1631, part 1)

The main objectives of this research were to improve the understanding of the characteristics of the grease emission and heat generation from electric countertop appliances, and to determine the amount of grease particulate/vapor production as well as sensible and latent heat gains from 20 commercial electric countertop appliances under cooking conditions. The grease particulate and vapor were captured by a Type II hood, and the concentrations were measured using EPA Method 5 in the exhaust duct under an exhaust flowrate of 0.24 m3/s (500 cfm). An energy balance protocol was used to determine the heat generation of these appliances during both idle and cooking conditions. The results indicate that the rate of grease particle and vapor emissions concentration for the 20 appliances tested ranged from 0.12 to 8.27 mg/m3. Only three appliances, the hot plate range, rapid cook oven (cooking with chicken wings or pizzas), and hot dog roller, generated more than 5 mg/m3 of grease at 0.24 m3/s (500 cfm) exhaust flow rate (i.e., 1.18 mg/s in emission rate), which is the threshold of the requirement to use a Type I hood by ASHRAE Standard 154 and UL 710B. The grease particulate matter caught by the EPA Method 5 was itemized by weight and analyzed as follows: filter catch, probe (acetone) catch, impinger (DI water) catch, and solvent extract (dichloromethane). The cooking sensible convective heat had a similar trend as the cooking energy consumption rate, except for the deep fryer and steamer countertop. However, the cooking latent convective heat depended more on the food material and whether or not steam was used to heat the food. The largest cooking latent convective heat was given by the steamer countertop, and the lowest was given by the hot plate and rice cooker. The effects of the duration of the test and the cooking time on the test results were also studied. It was found that three replicate tests with about 40 minutes each could generate similar reults as a 4-hour long test, hence a longer test duration (such as the 8-hour cooking test specified in UL 710B) may not be necessary. The study provides previously unavailable data of grease emission and heat generation rates for the design and analysis of kitchen spaces with countertop electrical appliances. They are used to update the current Table 5A; Recommended rates of radiant and convective heat gain from unhooded electric appliances during idle (ready to cook) conditions of chapter 18 in the ASHRAE Handbook of Fundamentals.

Caveats and technical challenges in performance evaluation of activated carbon (AC) and non-AC filtration for NO2 abatement toward energy-efficient and healthy ventilation

As the awareness of public health/safety becomes important and the desire to provide clean/safe indoor air in a sustainable way increases, air filtration technology has become essential at urban built facilities, which are challenged by significant outdoor air pollution due to dense population and heavy traffic. To provide comparable/objective data for designers and professionals of gas-phase filtration equipment in HVAC systems, it is important to understand the performance and characteristics of possible filter medium candidates within a reasonable testing period at low levels of target hazard concentration (typically, ∼0.05 ppm). The present study investigated the 2000-time scale-down evaluation evidence and its behind reasons between practical high-concentration tests (∼100 ppm NO2) and actual low-concentration ones, and investigated potential dangers identified during the study in utilizing activated carbon (AC)-based virgin filter media in indoor applications due to unexpected NO-desorption phenomenon. Six filter media of AC-based and non-AC with different type/pellet/shape/size/target compound were selected and tested for abating NO2 mainly originated outdoors. A multi-channel simultaneous testing system was utilized for similar standard testing conditions. The study findings provide previously unavailable experimental data and new insight into the behavior of widely used filtration media against NO2 for the enhancement of urban resilience.

Laboratory comparison of relative performance of gas phase filtration media at high and low O3/NO2 challenge concentrations (ASHRAE RP-1557)

To guide the selection and design of air filter/cleaning devices for improving indoor air quality (IAQ), it is important to be able to assess the performance and characteristics of filter media within a reasonable/practical testing period for low concentration conditions (∼50 ppb) under which they are applied. Our study objectives were to investigate whether filter media showing good performance at high concentrations per ASHRAE Standard 145.1 (ASHRAE 2008) would also perform well at low concentrations, typically indoors, and to explore whether and how existing models for filtration media beds can be applied to predict and extrapolate the experimental performance results obtained under high concentrations. Six filter media having different filtration properties, pellet shape and size, and target compound were selected for this investigation. Experiments were performed at both high (∼1 ppm/100 ppm) and low (∼50 ppb) levels of O3/NO2 concentration for all media selected. Existing models were evaluated for the feasibility of data extrapolation from high to low concentration conditions. The results showed that (1) the relative performance of filter media at high concentration was qualitatively indicative of that from the low concentration results and (2) no existing models were suitable for any media having major catalytic removal characteristics for the cases studied, and an improved mechanistic model needs to be developed.