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Indoor Air Quality Modeling
The Indoor Environment Management Branch has developed an IAQ model for analyzing the impact of sources, sinks, ventilation, and air cleaners on indoor air quality. Early versions of the model allowed calculation of indoor concentrations as a function of time. The model incorporates the latest results from EPA research on sources, sinks, ventilation, and air cleaners. The model predictions have been compared with results of test house experiments and the agreement between model predictions and experiment have been very good. The latest published version of the computer model, called RISK, is designed to allow calculation of individual exposure to indoor air pollutants from sources. The model is designed to calculate exposure due to individual, as opposed to population, activity patterns, and source use. The model also provides the capability to calculate risk due to the calculated exposure. Risk is calculated using a risk calculation framework developed by Naugle and Pierson (Naugle, D.F., and T.K. Pierson. A framework for risk characterization of environmental pollutants. Journal of Air and Waste Management Association, Vol.41, P. 1298. 1991.).
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. The concentration/time profiles are then combined with individual activity patterns to estimate exposure. The model allows analysis of the effects of air cleaners located in either/or both the central air circulating system or individual rooms on IAQ and exposure. The model allows simulation of a wide range of sources including long-term steady-state sources, on/off sources, and decaying sources. Several sources are allowed in each room. The model allows the analysis of the effects of sinks and sink reemissions on IAQ.
The model has recently been revised to allow improved analysis of particulate matter and multiple pollutants.
The results of test house experiments are compared with model predictions. The agreement between predicted concentration/time profiles and the test-house data is good. The model is designed to run in the MS-Windows operating environment.
Two Power Point presentations describing the model are available for download.
RISKPresentation1.zip (322 Kb)
RISKPresentation2.zip (692 Kb)
A paper describing use of the model for particulate modeling is available
for download here.
PMModel.zip (152 Kb)< br />
Documentation for the model is provided here.
RISKDocs.zip (1,936 Kb)
The model files are provided here.
RISKV19.zip (16,965 Kb)
These files are in zip format and require an unzip program. Two free programs
are Braxio FreeZip! and DS
Software FreeZip.
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:
- GPS.EXE is a general purpose IAQ simulation program with a rich library of indoor source models. It also handles chemical reactions.
- VBX.EXE implements four models for VOC emissions from solvent-based indoor coating materials. The built-in VOC property database simplifies the simulation process.
- SPILL.EXE contains three models for unstrained, small-scale solvent spills in the indoor environment.
- SLAB.EXE implements a mass transfer model for VOC emissions from building materials.
- PM.EXE is for indoor particulate matter (PM). It considers such factors as penetration of outdoor PM, emissions from indoor sources, deposition, ventilation, and filtration.
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. To download the IAQX software package, click HERE to download the IAQX model.
PARAMS 1.0
This Microsoft Windows-based computer program implements 30 methods for estimating the parameters in indoor emissions source models, which are an essential component of indoor air quality (IAQ) and exposure models. These methods fall into eight categories:
- the properties of indoor air,
- the first-order decay rate constants for solvent emissions from indoor coating materials,
- gas-phase, liquid-phase, and overall mass transfer coefficients,
- molar volume,
- molecular diffusivity in air, liquid, and solid materials,
- solid-air partition coefficient,
- vapor pressure and volatility for pure organic compounds and petroleum-based solvents, and
- the properties of water. Potential users include those who develop or use IAQ and exposure models, and those who develop or use quantitative structure-activity relationship (QSAR) models. In addition, many calculations are useful to researchers in areas other than indoor air quality. Users can benefit from this program in two ways: first, it serves as a handy tool by putting commonly used parameter estimation methods in one place; second, it saves users time by taking over tedious calculations.
Download the program and documentation. To install the program, run Setup.exe.