Sunday, February 1, 2015

Dr. Zhishi Guo and the Programs IAQX, PARAMS v1.1 and More

I can count the folks that I know who have provided free, user-friendly modeling programs in the service of human health exposure/risk assessment on the fingers of my two hands. Dr. Zhishi Guo is one such person. He retired from US EPA last March and is currently serving as the Deputy Editor for journal Indoor and Built Environment while also doing some consulting. Last week this blog highlighted one of his programs, i-SVOC, as an important tool. I found it to be a remarkable piece of freeware with a very slick interface that attempts to determine the time course and fate of any semi-volatile organic compound (SVOC) of concern in all the various compartments (sources, sinks, settled dust and airborne particulate matter) extant indoors.

Although I have yet to really put it through its paces, Shen Tian, P.E. Environmental, Health and Safety Engineer at Bayer Material Science, who initially identified it to me, has worked with i-SVOC and reports that it requires a number of input variables to feed it properly. Shen found that another program from Dr. Guo, PARAMS 1.0 can be used to estimate quite a few of the parameters required for input. Using a Google search I had trouble locating a link for PARAMS 1.0 that was not broken. I emailed Dr. Guo asking for his help. He responded:

“Last year, I updated programs IAQX and PARAMS to version 1.1 for compatibility with the Windows 7 and 8. The installation files for the new version can be downloaded from”.

I checked it out and indeed there is a wealth of freeware and information on this page. I downloaded everything I could from it. The descriptions on this page for the three programs offered on it are reproduced below:

IAQX v1.1: 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. The IAQX package consists of five stand-alone 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.

PARAMS 1.1: 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 seven categories:

1. the properties of indoor air,
2. the first-order decay rate constants for solvent emissions from indoor coating materials,
3. gas-phase, liquid-phase, and overall mass transfer coefficients,
4. molar volume,
5. molecular diffusivity in air, liquid, and solid materials,
6. solid-air partition coefficient, and
7. 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.

RISK: The latest published version of the RISK computer model is designed to allow calculation of individual exposure to indoor air pollutants from sources. The model runs in the MS-Windows operating environment and 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.

Even as someone with a very keen and long-standing interest in inhalation exposure modeling, I must admit that I was only vaguely aware of the availability of these tools. Along with i-SVOC, they form a remarkable legacy for the work of Dr. Guo and his colleagues. I am highlighting them here to point out their existence in the hopes that more folks will use them. We can only hope that Dr. Guo continues to stay active in the science and that the EPA will continue to sponsor and encourage exposure assessment scientists of his caliber.


  1. Your post is very nice. useful information. Thanks for sharing.
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  2. Hello Dr. Jayjock,

    I went to your link to download the updated i-SVOC software, but a "Page Not Found" error came back. I've been trying to find a download for this software for a few weeks now without any success. I would greatly appreciate it if you could please email me at with more information.

    Matthew Megill

  3. please i need someone to recommend a book for me on IAQ. I dont really understand IAQX and i want to learn it. Thanks in advance

  4. please i need someone to recommend a book for me on IAQ. I dont really understand IAQX and i want to learn it. you can email me on Thanks in advance

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