B. Fleckner, D. Cortes, B. Epstien, E. Horner, Air Quality Sciences Inc., Atlanta, GA.
Industrial hygienists often use chemical and mycological data to resolve the most complex indoor environmental quality (IEQ) complaints. Data trends develop over time, and it becomes possible to determine what can be considered the more common pollutants and how they may affect the indoor environment. Chemical analyses appropriate for non-industrial environments, such as USEPA methodologies, can yield hundreds of unique compounds in a given environment. In this review, data obtained from more than 300 different building studies will be summarized. For example, toluene is the most frequently measured VOC. The most common odorants include terpenes, amines, and carboxylic acids. Between 30 and 150 different VOCs are identified in most buildings. Identification of their possible sources is of the utmost importance in remedying an IEQ concern. Review of mycological analyses provide general trends with regard to common outdoor fungal mixtures and those that indicate moisture problems in indoor spaces. Fungi that are not prevalent in outdoor air generally should not be dominant in indoor spaces. Common leaf surface-type (phylloplane) fungi such as Cladosporium cladosporioides or Alternaria alternata comprise many samples collected in outdoor locations. Alternatively, common indoor pollutants generally consist of soil-type fungi such as various Penicillium spp. (e.g. P. chrysogenum, P. citrinum) or Stachybotrys chartarum. IEQ complaints can be addressed more readily with a greater understanding of the contaminants present in the environment.
A. Ames, D. Newcomer, S. Milz, B. Harrington, M. Bisesi, F. Akbar-Khanzadeh, Medical College of Ohio, Toledo, OH.
Air sampling was conducted at four fitness facilities over the course of 12 days for chemical, biological, and comfort parameter components. Sampling was performed outdoors and at five indoor areas: office area, daycare, pool, locker room, and the fitness center. Samples were collected in five period intervals throughout the day representing the baseline, peak, and off-peak times. Real-time monitoring and sorbent tubes were used for detection and monitoring of chemical contaminants and comfort parameters. Air samples for bioaerosols were collected using a single-stage Andersen impactor with Tryptic Soy Agar with 5% sheep blood for bacteria and Potato Dextrose Agar for fungi. Resulting concentrations of bacteria and fungi were determined, as well as the biodiversity. In general, chemical contaminants and comfort parameters were statistically different between area, time periods, and location. Correlation between carbon dioxide concentration and the number of building occupants was identified, as well as a relationship between traffic density and carbon monoxide concentration. In general, bacteria and fungi were statistically different between areas, time periods, and locations. The mean concentration of bacteria for the areas ranged from 84 cfu/m3 in the pool area to 563 cfu/m3 in the locker room. Gram-positive cocci were the predominant bacteria found with the exception of outdoors and the pool area where Gram-positive rods were predominant. Bacteria concentrations were significantly higher indoors compared to outdoors and in all other areas compared to the pool area. The mean concentration of fungi for the areas ranged from 95 cfu/m3 in the pool area to 580 cfu/m3 outdoors. Fifteen different genera of fungi were identified, 10 of which were only found indoors. Predominant genera identified were Cladosporium, Penicillium, Fusarium, and Rhodotorula.
T. Schoonover, A. Li, L. Conroy, P. Scheff, Q. Zou, University of Illinois at Chicago, Chicago, IL.
PAHs are ubiquitous multisource indoor air contaminants. Many are known or probable carcinogens. Therefore, it is important to understand indoor PAH emission sources and related source activities. Indoor and outdoor PAHs were monitored at 10 Chicago homes for 14 months. Sixteen PAHs were collected and analyzed. Home infiltration (hr-1) was assessed for each sampling event using two models, a statistical and an occupant generated CO2 tracer gas model. The statistical model is a function of indoor and outdoor temperature difference and wind speed while the CO2 model uses the slope of the decay curve to estimate infiltration. CO2 tracer gas infiltration results ranged from 0.03 to 0.64 hr-1 with a median of 0.14 hr-1. Infiltration estimates were combined with simultaneous indoor and outdoor PAH concentrations to generate indoor PAH emission rates. Component PAHs were partitioned into gas and particle phases. Particle-related PAH penetration was determined to be 0.25 from the slope of the lower edge of plotted concentrations. Particle removal efficiency of 0.2 hr-1 was applied to particle phase PAHs based on research done on 0.3–0.5 µm particles. Resulting PAH total indoor emission rates ranged from 30 to 36,400 ng m-3 with a median of 3074 ng m-3. Home characteristics, occupancy rates, and activities were obtained from resident surveys. Positive indoor PAH emission rates were combined with indoor occupancy rates and other reported activities to generate indoor PAH emission factors. PAH total emission factors for all sampling events were 1.2 ng m-3 per occupancy minute and 3.9 ng m-3 per cooking minute. Home indoor emission factors ranged from 0.6 to 7.6 ng m-3 per occupancy minute and from 5.2 to 135 ng m-3 per minute of cooking. PAH total emissions ranged from 0.6 ng m-3 for fall to 1.3 ng m-3 for spring per occupancy minute.
F. Boelter, D. Podraza, M. Reese, Boelter & Yates Inc., Park Ridge, IL.
Vapor intrusion exposures have focused on evaluating and mitigating exposures in residential settings. Typically, a residential setting utilizes indoor air quality guidelines and mitigation techniques fashioned after radon venting systems. Vapor intrusion exposures in occupational settings have, in principal, been deferred to OSHA. The re-development of former industrial Brownfield sites for non-industrial uses warrants evaluation to determine the appropriateness of applying OSHA standards to vapor intrusion-related exposures. OSHA standards may be appropriate in certain occupational settings (e.g. industrial) where chemical exposures are expected and vapor intrusion contribution may be indistinguishable from background levels. However, are the OSHA standards appropriate for other non-residential settings (e.g. office or retail) where chemical exposures are not expected or normally part of the workplace. Using case studies, this paper will present a discussion of the appropriateness of applying OSHA standards to vapor intrusion exposures in occupational settings. Risk-based indoor air levels as well as soil gas and groundwater screening levels developed in accordance with the U.S. EPA Vapor Intrusion Guidance and Human Health Risk methodologies will be presented for occupational settings where OSHA standards may be inappropriate. Implications will be examined for sites where closures have already been obtained from regulatory agencies.
D. Bissing, Health Science Associates, Los Alamitos, CA.
Indoor air quality has become an increasingly significant portion of industrial hygiene investigations. During investigations of homes and work environments for indoor air quality purposes, settled or airborne particulate matter including fibers is often perceived to be the irritant causing the problem. Though quantitating the amount of material present can be done gravimetrically, this does not answer the question as to the physical components of the particulate. Characterization using a variety of analytical techniques can often be problematic and cost prohibitive, the amount of bulk material may be limited, standard analytical techniques for industrial situations often don’t apply, such as analysis for metals or acid fumes, and advanced microscopic techniques such as SEM or TEM can be uninformative as well as very expensive. This presentation will discuss how using standard microscopic techniques, characterization of this particulate matter can be done in a thorough, rapid, and cost-effective manner. Though there are limitations to this technique, the information that can be obtained is often very useful. This technique can be applied to air, tape, bulk, and microvac samples. The basic physical components of the particulate can be identified or described. Quantitation can be a visual estimation of percentage or an actual count. Often, knowing this information can identify the problem or clarify the perception of occupants or employees as to the health effects or source of the particulate matter. In conclusion, though not applicable in every situation, this technique can be a useful tool in investigations.
C. Jenkins, MACTEC Engineering and Consulting Inc., Peoria, IL.
This presentation is a compendium of real-world HVAC system malfunctions, improper applications, and set points and common maintenance items that affect indoor environmental quality. Malfunctioning or improperly operated HVAC systems can result in poor fresh air exchange and thermal discomfort, known to be two of the leading causes of indoor environmental quality complaints. The case studies to be reviewed will share real-world building mechanical systems and common problems associated with these systems.
The industrial hygienist must be able to discuss HVAC system components and their operation with building engineers and facility managers to ascertain if the mechanical systems are the source of IEQ complaints. An industrial hygienist with an understanding of the systems and their operation can measure the systems efficacy at different points to determine if the air exchange rate is adequate to control bio-effluent buildup. The industrial hygienist can also measure and evaluate the system’s ability to control water vapor and temperature.
The goal of this presentation is to provide industrial hygienists with an understanding of the mechanical components that comprise a facility’s HVAC system; the nomenclature of the components, common problem areas encountered that affect indoor environmental quality, and different measurement methods utilized to determine the system’s efficacy. These tools shall enable the industrial hygienist to identify areas of concern and communicate corrective actions to building engineers and facility managers. Therefore, the industrial hygienist can more effectively diagnose indoor environmental issues and provide corrective action to correct deficiencies.
G. Walsh, Bell Helicopter, Ft. Worth, TX.
An increasing number of complaints of breathing problems, allergies, and adult on-set asthma by instructors and students at an aircraft maintenance school over several weeks generated an indoor air quality investigation requested by the director of training.
Students and instructors were complaining about headaches, lethargy, tearing
of the eyes, and scratchy throat. An international student was present and was
taken to the emergency room of a local hospital to be checked out. One of the
instructors went to the doctor and was told he had similar symptoms to
Legionnaire’s Disease.
The number of students per classroom ranges from 6 to 15. The curriculum
consists of highly technical material.
Four classrooms were the focus of the investigation. The challenge was to determine the source of the respiratory problems and design engineering controls when the source was determined.
The investigation began with looking for a source for Legionella to develop since one of the instructors had similar symptoms, according to his doctor. The components reviewed were HVAC system, plumbing, cooling towers, evaporative condensers, fluid coolers, humidifiers, and direct and indirect evaporative air-cooling equipment. Legionella was ruled out because a source was not available for growth.
Maintenance employees were interviewed regarding the HVAC system. It was learned that each classroom had its own air-supplying unit located in the ceiling. Each unit had a supply air and return located in the ceiling. The evaporative coil units recirculated the same air.
Two outside air units were placed on the roof. The total airflow is 4000 CFM. Each classroom receives 150–200 CFM. ASHRAE states each person should receive between 15–20 CFM of fresh air.
Benefits to industrial hygiene practitioners would be to look at all the possibilities for a problem source. Engineering decisions made in the past can create issues in the present.
R. Cussen, CNA, Kingston, MA.
“It’s too cold” and “it’s too hot” have ranked either #1 or #2 in all polls conducted by the International Facility Management Association, whereas poor indoor air quality ranked # 6 in the latest poll. This paper presents an association between the two problems. Thermal concerns have traditionally been the major concern expressed by office employees. Personal experience in hundreds of office IAQ investigations has shown that well-intentioned, but inappropriate, system adjustments made to satisfy thermal concerns often lead to IAQ problems. An improper HVAC system adjustment in reaction to occupant thermal complaints is presented as an initiating cause of many office IAQ problems. The ability to recognize, evaluate, and correct common, but improper, HVAC primary air system flow and distribution problems is proposed as a necessary tool for most office IAQ evaluations.
When thermostat adjustments do not satisfy concerns, the occupant or a maintenance technician may make adjustments that are often based on a rudimentary understanding of system operations. Initial adjustments often involve primary HVAC airflow supply and distribution restrictions. Such adjustments may lead to a temporary correction of the problem in the immediate area. However, experience indicates that such adjustments frequently lead to thermal complaints in other nearby areas. This sequence can then be repeated. Eventually, restrictions on airflow leads to system imbalances, an increase in thermal complaints, an increase in “cold air dumping,” a decrease in outdoor air supply, and, eventually, poor air quality complaints.
Commonly encountered adjustments that cause primary airflow restrictions include: reducing VAV box minimum air flows, reducing primary airflow to perimeter fan powered or induction units, blocking diffusers or closing register supply outlets, reducing economizer or outdoor air damper minimum set-points, etc. The ability to assess these problems, as well as “cold air dumping,” will be reviewed.
D. Salzberg, C. Feigley, University of South Carolina, Columbia, SC; A. Salzberg, Quantitative Analysis Inc., New York, NY.
Outdoor air exchange rate (Qo) is one of the most critical determinants of room air quality, yet the performance of methods for estimating Qo has received little attention. Here such a method for estimating Qo in occupied rooms using indoor and outdoor CO2 concentrations (CMB method) was developed and refined using simulated schoolroom CO2 data. It was then applied to actual data collected from two schools.
Simulated data were generated for four factorial combinations: two Qo values and two emission rate (G) values. The CO2 mass balance equation was linearized and Qo was estimated by regression. Refinements considered included: intercept/no intercept, smoothing the occupancy variable, and selective use of data (entire school day, occupied periods only, and unoccupied periods only, e.g. lunch and recess). The best method performance was found for no intercept, smoothing, and unoccupied room; errors for the four Qo-G combinations ranged from -4.08 to 0.63% (RMS error = 2.1%). The second-best method performance was found for no intercept, smoothing, and entire school day, which had errors ranging from –6.21 to 0.12% (RMS error = 3.3%). Use of data from the entire school day or from exclusively occupied periods allowed estimates of both G and Qo, but tended to underestimate both parameters.
The CMB method has several advantages. Estimates represent air exchange over time periods of any length, can be made while the room is occupied, and include the effects of all air exchange pathways. The data required can be obtained easily and unobtrusively.
K. Good, Battelle, Columbus, OH.
Like occupants in homes and office buildings, aircraft passengers are exposed to a mixture of outdoor air and recirculated air. However, aircraft occupants experience much higher occupant density and do not have the ability to leave or control their environment. These differences, along with increased air travel, have resulted in increased awareness and concern regarding aircraft air quality. Although numerous studies have examined aircraft air quality, it is beneficial to understand the transport and fate of gaseous or airborne contaminants. For a structure, examining contaminant sources, transport, and removal is often done with multizone modeling, an analysis technique that uses a zonal representation of a structure to estimate pressure differences and the resulting airflow.
In the work presented here, the multizone modeling software CONTAMW was used to build models of narrow and wide-body commercial passenger aircraft. These models incorporated physical characteristics of the aircraft, such as size and layout, and also specific operational characteristics (e.g., airflow rates, mixing ratios) of the environmental control systems. Using these models, the airflow-driven migration of indoor contamination, such as pathogens or odors, from a point source to the rest of the aircraft was estimated. Similarly, the models were used to assess the use of engineering controls to mitigate hazards. For example, using these models to simulate the introduction of smoke into an aircraft, it was possible to examine the effect of filters on smoke concentration and persistence. Additionally, potential mitigation techniques, such as turning off the recirculation, increasing flow of outside air, and venting the cabin were modeled to examine contaminant removal.
The results will show how multizone modeling tools can be used to assess contaminant transport within passenger aircraft and to estimate how engineering controls can be used to mitigate the effects of contaminants.
S. Tamanna, M. Ahmed, E. Lee, C. Feigley, J. Khan, University of South Carolina, Columbia, SC.
Assessment of exposure in industrial hygiene is an important concern. In order to perform contaminant exposure assessment in a workroom, it is necessary to predict the steady state concentration distribution in a room as a function of room-air exchange rates and ventilation air inlet and outlet locations. Existing model equations do not always predict the spatial concentration variations to the desired accuracy. As a result, in an alternate approach, the analysis of flow field and assessment of concentration in the room is determined by computational fluid dynamics simulations with fine grid. This approach can be computationally expensive and very time-consuming, particularly for three-dimensional cases. Researchers in the past have studied multi-zonal method and even coarse grid (for 2-D cases) CFD simulations to minimize the computational cost at the same time keeping the accuracy of predicted results within reasonable error limits. In this paper, a similar approach has been taken where 3-D CFD simulations are performed for various ventilation flow rates and relative contaminant source, inlet, and outlet locations of the ventilation air. In order to reduce the time requirement for CFD analysis, coarse grid simulations have been studied for three cases: two-dimensional, semi-two dimensional, and three-dimensional, and these data have been compared with the fine grid CFD simulations. The analyses show that two-dimensional and semi-two dimensional cases can have good agreement with fine grid solutions for both velocity profile and concentration estimates. In three-dimensional cases, the coarse grid simulation method provides reasonable results only in rooms that are geometrically symmetric. For most other rooms, CFD results do not show satisfactory agreement in assessing concentrations, whereas velocity profiles show better agreement than concentration in three-dimensional cases. This paper presents several CFD results with varying grid sizes and some experimental results to demonstrate the validity of the conclusions obtained.
M. Ahmed, S. Tamanna, E. Lee, C. Feigley, J. Khan, University of South Carolina, Columbia, SC.
The relative location of air inlets and exhausts ventilation ports, presence and locations of heat and contaminant producing sources, and the presence of flow obstructing furniture are some of the important factors which affect the distribution of contaminant concentration in a workroom. This paper presents an extension of our previous work where several different inlet and exhaust locations without furniture presence were investigated. In this paper we have attempted to determine if the presence of furniture and heat-producing sources affect the optimum inlet and exhaust locations which was previously studied without the presence of furniture. Room concentration patterns for a workroom were explored by computational fluid dynamics simulations for various inlet locations, exhaust locations, with furniture and dilution air flow rates. Thermal effect for worker presence, computers, and lights on were also investigated. Average contaminant concentrations were calculated for the entire room, the breathing zone plane, and the near-source breathing zone.
It was found that the presence of furniture does not affect the optimum location of inlets and exhausts provided the furniture does not directly obstruct the exhausts. For wall jet inlets when the exits are on the right or left sidewalls, contaminant concentration is affected by the presence of furniture. This is because the incoming jet is diverted by the furniture. When the inlets are on the sidewalls, presence of furniture results in higher contaminant concentration but the reverse is true for ceiling inlets. Light sources present in the ceiling appear to have less effect on the concentration, because the buoyant plumes created by the light tend to not affect the rest of the flow, whereas the presence of computers on a desk did affect the concentration if the buoyancy-driven flow changed the overall flow pattern.
Posted May 30, 2004