196
LIMITATIONS OF CARBON DIOXIDE AS AN INDEX OF INDOOR AIR QUALITY.
C. Feigley, D. Salzberg, C. Toole, University of South Carolina, Columbia, SC.
Carbon dioxide (CO2) has been used extensively as a surrogate for indoor air contaminants related to human occupancy in buildings. Recently, health and perceived air quality have been shown to be closely related to ventilation rates, but roughly half these studies failed to detect a significant association of these outcomes with CO2 levels. One possible reason that CO2 is not always predictive of poor IAQ outcomes is that many etiologic agents are present as airborne particles and thus are influenced by sources, transport processes, and removal mechanisms quite different from those influencing CO2.
Here the effect of indoor air recirculation through an HVAC system is explored over a range of contaminant removal efficiencies. The greater the removal efficiency, the lower the resulting room concentration. In addition, concentration data are presented for CO2, particulate by particle size, and airborne markers of bacterial contamination from three elementary schools. For the 21 individual classrooms studied, CO2 concentrations were not good predictors of particulate or bacterial marker concentrations. Thus, irritation and allergic symptoms possibly related to these components likely would not be associated with CO2 concentrations at reasonable filter efficiencies.
197
INDOOR AIR QUALITY IN RESTAURANTS AFTER ENACTMENT OF CLEAN INDOOR AIR
ORDINANCES.
A. Ames, Delta Environmental Inc., Perrysburg, OH; S. Milz, F. Akbar-Khanzadeh, Medical College of Ohio, Toledo, OH.
Indoor air quality was studied in four restaurants to evaluate the effectiveness of recent clean indoor air ordinances. Two restaurants were nonsmoking while the other two contained a designated smoking room. The levels of ultrafine particulates, carbon dioxide, ambient temperature, and relative humidity were measured using direct reading instruments. The levels of ultrafine particulates ranged from 6870–25,840 particles per cubic centimeter (pt/cm3) in the nonsmoking restaurants; 11,090–180,800 pt/cm3 in the nonsmoking rooms of the smoking restaurants; and 76,990–143,100 pt/cm3 in the designated smoking rooms of smoking restaurants. Ultrafine particle levels were significantly higher in the smoking restaurants than in the nonsmoking restaurants. Carbon dioxide levels ranged from 319–2206 ppm in the nonsmoking restaurants, 719–3860 ppm in the nonsmoking rooms of the smoking restaurants, and 758–4505 ppm in the designated smoking rooms of the smoking restaurants. Only 36.6% of carbon dioxide measurements met the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) criterion level of 1000 ppm (39.7% of the measurements in the smoking restaurants and 34.2% of the measurements in the nonsmoking restaurants). Within the smoking restaurants, measurements from the designated smoking rooms only met the criterion 20.8% of the time, while the measurements in the nonsmoking rooms met the criterion 52.9% of the time. The majority of temperature and relative humidity readings in these restaurants were within ASHRAE-acceptable thermal environmental conditions. The results of this study show that higher levels of ultrafine particles and carbon dioxide are present in the smoking restaurants than in the nonsmoking restaurants, which may be attributable to tobacco smoke. This may be an indication of the lack of expected effectiveness of the clean indoor air ordinances.
198
VENTILATION RATES AND CO2 LEVELS IN A HOTEL IN THAILAND.
W. Phanprasit, V. Boonyayothin, Mahidol University, Bangkok, Thailand.
The objectives of this study were to investigate the correlation between the factors that influence IAQ and IAQ complaints/symptoms; and the suitability of the recommended standards for those factors to a hotel in Thailand.
Twenty-eight conference rooms, 15 dining rooms, 14 lobbies, and 43 bedrooms in 23 hotels were studied. The concentration of CO2, CO, dust, TVOC, and %RH and temperature were measured. Six hundred eighty-six staff and guests of those hotels were interviewed for complaints/symptoms related to IAQ. The correlation between each factor and complaints/ symptoms was analyzed. Only the pairs with statistical significant correlation were continuing analyzed for prevalence rate ratio (PRR) and prevalence rate (PR). People who had more than or equal to three complaints/symptoms were classified as “have complaints/symptoms,” and those who were in the areas with the studied factors higher than their standards were considered as “high-exposure” and “high-cfm” for those in the areas that complied with ASHRAE Standard 62-1999.
The results showed that dust, TVOC, and CO concentrations and %RH and temperature were not significantly correlated with complaints/ symptoms; only CO2 levels and ventilation rates were. All PRRs indicated that the “high-exposure” and “low-cfm” group had IAQ complaints/symptoms more than others significantly (p-value = 0.05). The PRs among low-exposure groups to CO2 was 42.8%. While the PRs among high-cfm groups were 25.3% for conference rooms, 36.2% for dining rooms, 36.5% for lobbies, and 20.8% for bedrooms.
The conclusion was: People who were in the areas that did not comply with the IAQ recommended standards had higher risk of IAQ complaints/symptoms. In the complied areas the PRs were lower than ASHRAE’s definition of acceptable indoor air quality—80% of the people exposed do not express dissatisfaction with the indoor air quality. Thus, we may conclude that ASHRAE’s Standard 62-1999 is not appropriate for the hotel in Thailand based on the above definition.
199
PREDICTING CONTAMINANT CONCENTRATIONS ON COMMERCIAL PASSENGER AIRCRAFT: WHERE IS
THE CLEANEST AIR?
K. Good, Battelle, Columbus, OH.
Aircraft passengers, like the occupants of homes and office buildings, are exposed to a mixture of fresh (outdoor) and recirculated air. However, aircraft passengers experience much higher occupant density and do not have the ability to leave or control their environment. Although aircraft air quality has been the subject of numerous studies, being able to accurately predict the transport and concentrations of gaseous or aerosolized contaminants in aircraft is important because it could help develop and assess contaminant-related control strategies.
In the work presented here, the carbon dioxide concentration measured on a North American flight as part of an ASHRAE study is compared with the concentration predicted using a multizone airflow model of an aircraft. The model, which was built using the multizone modeling software CONTAMW, incorporates the physical characteristics of the aircraft (e.g., size, layout), the operational characteristics of the air-handling system (e.g., air flow rates, mixing ratios), and the characteristics of the flight (e.g., temperature, pressure, passenger load, and distribution). The data collected in the ASHRAE study is also compared to the concentration predicted by a steady-state ventilation equation. The findings show that the model prediction agrees strongly with the measured concentration (only 1% error), which is an improvement over the steady-state equation prediction (9.4% error). The multizone model was then used to predict the carbon dioxide concentration profile down the length of the aircraft. This predicted concentration profile can serve as a location-specific indicator of the concentration of other contaminants, helping to identify areas within the aircraft cabin containing “dirty air.” Strategies for improving air quality in these areas are proposed and their impact on air quality was assessed using the model.
200
A REVIEW OF THE CURRENT SITUATION: EFFECT OF FUEL TYPE AND AIR TREATMENT IN
RESIDENTIAL BUILDINGS ON RESPIRATORY ILLNESS.
E. Gatey, Manitoba Hydro, Winnipeg, MB, Canada.
To some there is a perception that natural gas fuel has a disproportionate affect on indoor air quality when compared to other fuels. In fact, each fuel source appears to have the potential to affect one aspect of indoor air quality or another. The aspect of air quality affected by each fuel is characteristic of the fuel and the conditions of use from PAHs released by burning wood to ultrafine particles generated by convection-type electric baseboards. Natural gas appliances produce NO2, which results in the potential to increase the incidence of respiratory disease. In addition, air treatments such as humidification and air conditioning may affect health outcomes in the indoor environment. Recent studies suggest two things about fuels: that atopics (persons with allergies) experience increased morbidity when exposed to natural gas appliances; and young women who cook on gas appliances are more likely to experience respiratory health effects. The European Community Respiratory Health Survey report, expected in 2004, is based on a sample large enough to establish causal factors for asthma including: type of fuel, crowding, social status, housing characteristics, occupation, and smoking. Considering early results of the survey, finding ways to reduce by-products of burning natural gas with more efficient burners or developing efficient ventilation systems for gas appliances might be a worthwhile effort for the natural gas industry. The owner of a low NO2 burner or gas appliance may be well rewarded for the effort.
201
EMISSIONS FROM BUILDING MATERIALS USED IN A NEW EXPERIMENTAL HOUSE.
A. Bartekova, P. Huelman, University of Minnesota, St. Paul, MN; C. Lungu, University of Minnesota, Minneapolis, MN.
A new pilot composite panel house has been built for low income families in St. Paul, Minn. The energy efficient house was built using a new technology that employs large amounts of oriented stranboard (OSB). It is known that wood composite materials could emit larger amounts of volatile organic compounds (VOC) that can induce a number of health effects for the occupants. The concentration of airborne organic contaminants in a new experimental house and the VOC emission profiles of the building materials and coatings used in the house have been assessed. Measurements were performed to determine formaldehyde, individual VOC, and total VOC (TVOC) concentrations using area air monitoring. The results show that TVOC can reach considerably high concentration levels (up to 2.3 mg/m3) during the first month after building completion. This is a function of both the composites panels and coatings as well as other materials and finishes in the house. The obtained TVOC concentration was higher than the recommended target comfort zone of 200–300 µg/m3. TVOC concentration in the house without mechanical ventilation was approximately two times higher than with ventilation. However, after six months since testing started, the TVOC concentration decreased to 0.455 µg/m3. The dominant classes of compounds detected in the monitored house were aromatics, alkanes, terpenes, and ketones. Building material and coating emission tests were conducted using a 55-liter environmental chamber. The laboratory results indicate that terpens were found mainly in the uncoated OSB samples (9.5% of TVOC emissions represented alpha-pinene) while N-decane (18%) and N-undecane (36%) are the most abundant components in the oil-based primer used as coating. The water-based latex was found to contain mainly benzene derivatives (30%).
202
PILOT STUDY TO EVALUATE VOLATILE ORGANIC COMPOUNDS (VOCS) IN DUST FROM INDOOR
SURFACES.
B. Epstien, A. Worthan, Air Quality Sciences Inc., Marietta, GA.
Indoor surface dust can be a useful tool in evaluating nonindustrial indoor environments. Historically, dust has been studied as a reservoir for numerous biological contaminants including molds, allergens, and endotoxin. Additionally, particle analysis using various microscopy techniques has been used to characterize organic and non-organic dust constituents. The purpose of this study was to determine the significance, if any, of dust as a reservoir for volatile organic compounds (VOCs). In the current study, dusts were evaluated from residential buildings to compare various sources indoors, e.g., comparing among different homes, and comparing among and between different surface types. Surfaces evaluated included: carpeted flooring, nonfloor surfaces, and upholstered furniture. Samples were collected from eight homes in one metropolitan area. Samples were collected onto 0.45 micron polycarbonate membrane filter cassettes attached to portable, high-volume vacuum pumps. Samples were analyzed via thermal desorption followed by gas chromatography/ mass spectrometry. Results were reviewed to determine total chemical load, specific chemical classes, and individual chemicals. Total VOC (TVOC) levels in all samples ranged from 181 to 4200 ug/m3. Carpet dust TVOC was generally lower than that found in other surfaces, with nonfloor surfaces (such as book shelves, tops of pictures and televisions, lamp shades, and cabinetry, among other surfaces) having the highest TVOC. Many distinct, individual VOCs were identified in each sample (from 20 to 100 individual VOCs), representing various chemical classes including aromatics, aliphatics, aldehydes, and acetates. Specific chemicals found were indicative of cleaning products (e.g., acetic acid, 2-butoxyethanol), fragrances (eucalyptol, linalool), and paints (e.g., Texanol, TXIB). Results suggest that analysis of dust for VOCs provides useful, historical data on residual chemicals from a variety of sources, and thereby potential exposures indoors.
203
THE STUDY OF APPLICABILITY OF ACTIVATED CARBON FIBERS (ACF) FOR REMOVAL OF
VOLATILE ORGANIC COMPOUNDS (VOCS) IN INDOOR ENVIRONMENTS.
H. Lu, N. Zimmerman, Purdue University, W. Lafayette, IN.
Indoor air quality is an issue of rising concern in the United States. Indoor VOCs contribute significantly to sick building syndrome, the symptoms of which include irritation of eyes, nose, and throat, erythema, mental fatigue, headache, nausea, and dizziness. This research focuses on examining the applicability of indoor VOC adsorption onto activated carbon fibers. The goals of this research were: (1) to examine the applicability and capacity of ACF for removal of selected typical VOCs at indoor concentrations, and (2) to develop suitable mathematical models for predicting breakthrough time and adsorption capacity of ACF.
Dilution air from house air was passed through a zero air generator to generate purified air which contains less than 0.1 ppm hydrocarbons measured as methane. Two common VOCs with different boiling points and different polarities, toluene and acetone, were tested. Different challenge levels of VOCs were obtained by diluting gas from calibrated cylinders with zero air. Adsorption capacities of activated carbon for the VOCs individually and in mixtures were tested in the concentration range of 100 ppb to 10 ppm with a contact time of 0.1 seconds. Air samples collected by activated charcoal tubes were analyzed by a Varian GC Analyzer equipped with a flame ionization detector. ACF has shown excellent adsorption capacities on toluene even in the ppb level with the 50% breakthrough time at 60 ppb being greater than two months. The results gained in this study show that ACF is promising for removal of indoor VOCs with long-term low concentration levels.
204
HIGH EFFICIENCY ADSORBENT FILTERS FOR REGENERABLE COLLECTIVE PROTECTION USING
PACKED BED + POLISHING SORBENT ARCHITECTURES.
A. Queen, Center for Microfibrous Materials Manufacturing, Auburn, AL; B. Tatarchuk, Auburn University, Auburn, AL.
Current collective protection equipment (CPE) designs for the removal of toxic industrial chemicals and military chemical agents utilize thick and inefficient packed bed designs. To achieve high levels of filtration, packed beds generally introduce large pressure drops into air management systems and make inefficient use of the sorbents they contain. A composite bed architecture presents a more efficient and lower pressure drop alternative to these systems.
A composite bed composed of large sorbent particles (0.6–1.7 mm diameter) followed by a polishing filter several millimeters thick can achieve high breakthrough time and high sorbent utilization with low total thickness and pressure drop. The polishing filter portion of the composite bed is composed of small, well-dispersed sorbent particles (10–250 µm) sinter-locked in a layer several millimeters thick of micron diameter fibers. The outlet gas from the packed bed immediately encounters the high contacting efficiency polisher which reduces normal inefficiencies associated with the mass transfer zone/critical bed depth. Overall 5-log breakthrough time is greatly increased as compared to a conventional packed bed.
Test data using a hexane challenge, and other simulants, have shown this arrangement capable of 5-log protection for 85 minutes (200 ppm hexane, 24.2 cm/s face velocity) at only 1.3” H2O pressure drop and 1.3 cm total bed thickness. Two CPE composite bed types have been evaluated, regenerable and single use/throwaway systems. Regenerable composite beds utilize micron diameter nickel fibers in the polishing layer and high-temperature sealant for regeneration via TSA, PSA, and PTSA. 5-log protection was observed after six regeneration cycles via TSA. Single-use/throwaway composite beds incorporate polymer fiber polishing filters into current COTS units. This approach yields high logs of removal and increased bed utilization by addition of a thin polisher to the back of an existing COTS unit.
Posted May 30, 2005