Facilities and Capabilities

Introduction

The Indoor Environment Management Branch (IEMB) of EPA's National Risk Management Research Laboratory has performed fundamental and applied research on indoor air pollution prevention and control since 1984. The initial emphases of the program were on characterizing sources of indoor contaminants, primarily volatile organic compounds (VOCs), using small chambers and a test house; indoor air quality (IAQ) modeling; air cleaner evaluation; and radon mitigation techniques for homes. In 1991, IEMB expanded its program to include evaluations of biocontaminant sources and control options, the implications of ventilation on IAQ, radon mitigation techniques for large buildings, and pollution prevention options. More recently, the program has focused on developing standard methods and models for specific classes of indoor sources (e.g., paints, cleaners, adhesives), developing methods for large chamber emission testing, and technology verification (e.g., air cleaners and office furniture). Currently, the program is also developing standard methods for evaluating environmental conditions that cause fungal growth, investigating antimicrobial agents, measuring emission factors for fungi, investigating the impact of ozone generators on VOCs, developing a model for decision-making regarding water-based cleaners used in schools, assessing the penetration of particulate matter (PM) into indoor environments, and characterizing indoor PM sources.

Click on the "Points of Contact" and "Biosketches" links to the left for a listing of IEMB staff members and their areas of responsibility.

This page describes IEMB's in-house and extramural programs. In-house research studies are conducted on a variety of bench-, pilot-, and full-scale test facilities in Research Triangle Park, NC. This Division's in-house test facilities include small environmental chambers, a large environmental chamber, a particle emissions chamber, an IAQ test house, and a pilot-scale ventilation and fine particle test facility. Biological static chambers and a biological dynamic chamber are available off site. A three-phase approach, chamber(s) model test house, forms the core of IEMB's in-house research program (Figure 1). This approach ensures that test methods, emission factors, and source/sink models developed are validated in a full-scale environment.

Figure 1 - Three-phase IAQ Research Approach

Source Characterization and Emissions Testing

Source characterization and emissions testing are conducted in small and large chambers to provide information on rates and composition of organic vapor emissions from various indoor materials over a wide range of measured environmental conditions representative of in-use conditions.

Small Environmental Chambers
IEMB has seven small environmental chambers (53-liter volume) (Figure 2), which can be used for both static (equilibrium) and dynamic (flow-through) tests. These chambers enable measurement of the emission rates of a wide range of potential contaminants from a variety of different products and materials that might be found in indoor environments.

The chambers are made of polished stainless steel, and are located in temperature-controlled incubators. A control and data acquisition system enables effective control of the temperature, relative humidity (RH), air exchange rate, and air velocity inside the chambers.

Gaseous compounds being emitted from the test material are measured in the off-gas leaving the chambers. Volatile organic compounds (VOCs) are collected using closed-loop or sorbent cartridges depending on the concentration. Sorbent samples are thermally desorbed prior to analysis by gas chromatograph. Samples are quantified using non-specific flame ionization detectors (FID) or electron capture detectors (ECD) and specific mass spectrometers (MS). Concentrations are computed based on mass detected and sample volume.

Studies performed in the small environmental chambers have included:

development of a standardized small chamber test method (ASTM-D5116-90);
characterization of VOC emissions from "wet" products such as waxes, stains, latex and oil-based paints, varnishes, and water-based cleaners;
characterization of VOC emissions from "dry" products, such as moth cakes, carpeting, vinyl flooring, dry-cleaned clothing, engineered wood products, and photocopied paper;
characterization of the adsorption and desorption rates for various air contaminants on indoor materials, such as carpets and drapes ("sink behavior"); and
development of a fundamental emission model to explain VOC emission rates from a variety of solid sources for which emission rates are controlled by mass transfer of the contaminant through the interior of the source.

Figure 2 - Flow schematic for IEMB's small (53-L) test chambers.

Large Environmental Chamber
The large chamber test facility (Figure 3) is a room-sized (30 m³) environmental chamber that is equipped with a clean air generation, air conditioning, and air distribution system. The chamber design enables researchers to investigate emissions from products or processes in the absence of confounding contaminants found in ambient air. The internal surfaces of the chamber are constructed of polished stainless steel to minimize surface adsorption. The internal surfaces of fans and air conditioning and air delivery system components are electro-polished to minimize surface adsorption and facilitate cleaning. The clean air supply system which is designed to provide up to 500 cubic feet per minute (CFM) of clean, conditioned air, incorporates coarse and high efficiency particulate air (HEPA) filtration and volatile organic compound (VOC) removal subsystems. A computer control system is employed to set, maintain, and record test conditions of temperature, pressure, relative humidity, and airflow rate. The facility has been designed for flexibility to meet many research needs. The system design allows researchers to operate the chamber in a static or stopped flow mode, in single pass mode where supply air is exhausted from the chamber, or in recirculation modes where some or all of the chamber supply air is circulated back to the chamber air supply. Types of studies that may be conducted in the full-scale chamber include:

development and evaluation of test methods to characterize emissions from whole products, assemblies, and processes (e.g., furniture, floor systems, cleaning, painting, and remodeling activities);
validation of scaleup factors used in IAQ models;
evaluation of air cleaners and interactions between multiple sources and sinks; and
investigations of chemical reactions in indoor environments.

Figure 3 - Large Environmental Chamber

Particle Emissions Test System

A stainless steel test chamber specifically designed for measuring fine particulate matter (PM) emissions is used for characterizing emissions from indoor sources. A diagram of the test system is shown in Figure 4. The air volume flow rate range of the system is 2800-85000 L/min (100-3000 cfm). One-pass air flow is typically used for PM emission tests, but recirculating air flow is also possible with the system. Air flow through the test chamber is automatically controlled with a PID (proportional/integral/ derivative) controller, a variable-frequency inverter drive that supplies electrical power to a blower, and an air-flow measuring station that provides feedback to the controller. The blower and controller are not shown in Figure 4. Air from the blower passes through a plenum, prefilters, and ULPA (ultra-low penetration air) filters to a test chamber where PM sources are tested. Chamber dimensions are 1.22 m (48 in.) wide x 1.83 m (72 in.) high x 2.13 m (84 in.) long. Air flows through the chamber, through a converging section, through a 180° bend, and then through a long, straight length of 25.4-cm (10-in.) diameter duct where isokinetic sampling probes are located. Air is either exhausted through a stack to outdoors or recirculated to the blower inlet.

The test chamber can be used for measuring fine PM emissions from indoor-environment non-combustion and small-combustion sources such as:

Cigarettes, cigars, incense, candles
Aerosol cleaning and consumer products
Vacuum cleaners and electric motors
Office equipment

Figure 4 - Particle Emissions Test System

Indoor Air Quality Evaluation and Prediction

The source/sink sorption and emission data measured in the chambers are integrated into an IAQ model. The computer model can be used for IAQ prediction, personal exposure simulation, and experimental design. Full-scale experiments are performed in an IAQ test house to verify the model predictions. The test house provides a realistic environment for testing the interactions between indoor air pollutant sources and sinks and ventilation characteristics.

IAQ Computer Model
A user-friendly IAQ model (called RISK) was developed for Windows-compatible computers. RISK uses a menu-driven fill-in-the-blanks user interface. The model uses data on source emissions, room-to-room air flows, air exchange with the outdoors, and indoor sinks to predict concentration/time profiles for all rooms. Based on the time/concentration curve and the individual activity pattern, RISK then calculates instantaneous and cumulative exposures. A database of common indoor sources, sinks, and ventilation systems is provided with the model. Default values for important model parameters are incorporated into the model to reduce the need for user input and make the model easier to use. The model also allows addition of new sources, sinks, and special building features. The concentration/time curves predicted by RISK are in good agreement with the concentration/time curves measured in several experiments.

The IAQ model has been used for

analysis of interactions between sources, sinks, and ventilation factors;
prediction of spatial and temporal distribution of indoor air pollutants in multi-room buildings;
assessment of individual exposure based on individual activity patterns, building features, and pollutant concentrations; and
evaluation of the effectiveness of IAQ control measures.

IAQX 1.0
IAQX stands for Simulation Tool Kit for Indoor Air Quality and Inhalation Exposure. It is a Microsoft Windows-based indoor air quality (IAQ) simulation software package that complements and supplements existing IAQ simulation programs (such as RISK) and is designed mainly for advanced users. IAQX version 1.0 consists of five stand-alone simulation programs. A general-purpose simulation program performs multi-zone, multi-pollutant simulations and allows gas-phase chemical reactions. The other four programs implement fundamentally based models, which are often excluded in the existing IAQ simulation programs. In addition to performing conventional IAQ simulations, which compute the time/concentration profile and inhalation exposure, IAQX can estimate the adequate ventilation rate when certain air quality criteria are provided by the user, a unique feature useful for product stewardship and risk management. IAQX will be developed in a cumulative manner and more special-purpose simulation programs will be added to the package in the future.

IAQ Test House (Rented)
The IAQ test house (see Figure 5 for floor plan) is an unfurnished, single-story, wood-framed house with a central heating and air conditioning system. The heated floor area of the house is about 120 m². The indoor temperature and relative humidity are monitored throughout the house. Air handler (furnace) flows are measured using hot-wire or inertial anemometers. Outdoor air exchange rates are measured using tracer gas techniques. VOC and particulate concentrations are determined over time and at several locations (rooms). Meteorological data are obtained from an on-site meteorological tower. All the data are analyzed and recorded using on-site computers.

Studies performed in the IAQ test house have included

effects of building features on indoor air and pollutant movements,
IAQ impact by VOC emissions from wood finishing products and moth cakes,
IAQ impact by dry powder carpet cleaning agents,
sink effects and their impact on the test house indoor air quality,
rate of particle deposition on interior surfaces,
penetration of ambient particles through individual types of openings,
effects of window openings on air exchange rate and particle penetration, and
rate of entry of gaseous combustion products.

Figure 5 - IAQ Test House

Indoor Air Biocontaminants

Biocontaminants such as fungi, bacteria, toxins (mycotoxins, endotoxins), and allergens have been recognized as the most common cause of building-related illnesses. Building materials that have become contaminated and sustain a population of biocontaminants are a significant source of indoor air pollution. The IEMB has worked cooperatively in the past with Research Triangle Institute (RTI) in this area. A capability to study factors that determine microbial growth, emission rates, and dispersion on building materials remains resident at RTI.

Biological Static Chambers (Off-Site)

The biological static chamber facility located at Research Triangle Institute (RTI) has been used to characterize biocontaminant (e.g., fungi and bacteria) growth on building materials in indoor environments. A schematic drawing of a static chamber is presented in Figure 6. Each chamber (32 x 39 x 51 cm) is equipped with three shelves, a small fan, a hygrometer, and a pan of saturated salt to maintain a specific RH. The chambers are placed in a dark, temperature-controlled, and HEPA-filtered room. Building materials to be tested are inoculated with specified microorganisms and placed inside the chambers to incubate in controlled environments simulating indoor conditions. Microbial growth on tested materials can be evaluated both qualitatively and quantitatively.

Factors investigated in the biological static chambers have included:

minimum moisture requirements for microbial amplification,
susceptibility of ceiling tiles to fungal growth,
comparison of the ability of duct lining materials to support fungal amplification, and
effectiveness of indoor climate control.

Figure 6 - Schematic (Side View) of a Biological Static Chamber

Biological Dynamic Chamber (Off-Site)

The room-size biological dynamic chamber, as shown in Figure 7, was designed to study the conditions and factors that influence biocontaminant emissions and dissemination. The chamber, a cube with inside dimensions of 2.44 m, was constructed with stainless steel walls and door and an acrylic drop-in ceiling. Temperature (15 to 32 °C) and RH (55 to 95%) control are provided through an air handler, conventional ductwork, and ceiling diffusers with an air circulation rate between 1.4 and 4.8 m³/min. A ceiling mixing fan is provided for experiments requiring additional mixing. Access to the chamber is through a door or a glove-wall and pass-through. The chamber was constructed within a cleanroom. The biological dynamic chamber is located at RTI.

On-going and past experiments conducted in the biological dynamic chamber include:

characterization of biocontaminant emissions and deposition,
evaluation of spore and antigen dissemination and dispersion,
evaluation of room-type and in-duct air cleaners for biocontaminant control, and
testing the effectiveness of cleaning and maintenance techniques.

Figure 7 - Schematic (Elevation) of the Biological Dynamic Chamber

Fine Particulate Research

As a result of recent studies indicating significant correlations of increased mortality and morbidity with increases in ambient fine particles, it has become even more important that we better understand personal exposures to fine particles indoors. Most people spend most of their time indoors, and the ones at greatest risk in the studies mentioned above spend nearly all their time indoors.

One of the major thrusts of IEMB's fine-particle research efforts is to determine the contribution to personal indoor exposure of fine particles that originate outdoors. The Division's two-compartment research facility is used to study the mechanisms by which fine particles in the outdoors penetrate into the indoor environment.

The facility consists of two, nearly identical, room-sized (19 m³) compartments. The two compartments are separated by a partition with a 0.61 x 1.22 m opening in which simulated air entry paths can be mounted. This facility is currently being used to verify mathematical models for penetration of fine particles through well-defined entry paths. It will be used later to measure particle penetration through openings created by installation of commercially available building components such as windows and doors. A schematic of the facility is shown in Figure 8.

Figure 8 - Schematic of Two-Chamber Research Facility

Air Cleaners Evaluation

In a cooperative effort with RTI, IEMB has developed a test facility and a standardized protocol to evaluate particulate air cleaners. The facility can test commercially and residentially sized cleaners with air-flow rates up to 3,000 acfm. A set of extensive evaluations of in-duct or central air cleaners for particulate matter has been completed using this facility. Commonly used air cleaners such as electrostatic precipitators, high efficiency filters, furnace filters, industrial-rated filters, and electrostatically augmented filters were included in the study. The test covered the particle diameter range of 0.01 to 10 µm. The evaluation included determining efficiency as a function of particle diameter for clean and dirty air cleaners and pressure drop or energy consumption. EPA's Environmental Technology Verification (ETV) program has used these methods to develop standard protocols to verify air cleaner performance. Verification testing is now underway.

Separately, an in-house program is underway to understand the performance of ozone-generating indoor air cleaners, and to understand the effect of these ozone generators on indoor ozone levels. This research will determine such factors as the ozone generation rate as a function of operating conditions for common ozone generators and the impact of the ozone generators' indoor pollutants. Research to date shows that ozone generators produce ozone and oxides of nitrogen. In the presence of reactive VOCs, use of ozone generators can result in increased concentrations of aldehydes and other oxygenated VOCs and fine particles.

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