The SimSmoke.Org website hosts on-line tools for simulating exposure to secondhand tobacco smoke in a variety of locations, including homes, cars, bars, restaurants, etc. The models can be executed from your web browser.

The U.S. federal government has created an in-house exposure simulation model for particulate matter with sophisticated sampling features.

From the paper abstract: "The US EPA National Exposure Research Laboratory (NERL) has developed a population exposure and dose model for particulate matter (PM), called the Stochastic Human Exposure and Dose Simulation (SHEDS) model. SHEDS-PM uses a probabilistic approach that incorporates both variability and uncertainty to predict distributions of PM exposure, inhaled dose, and deposited dose for a specified population."

U.S. Environmental Protection Agency model for predicting indoor air quality and exposure in multi-zone residential locations. Contains embedded empirical data inputs on air flows between rooms.

OpenFOAM is a sophisticated open-source framework for performing computational fluid dynamics (CFD) simulations.

From the website: "The OpenFOAM (Open Field Operation and Manipulation) CFD Toolbox can simulate anything from complex fluid flows involving chemical reactions, turbulence and heat transfer, to solid dynamics, electromagnetics and the pricing of financial options. OpenFOAM is produced by OpenCFD Ltd, is freely available and open source, licensed under the GNU General Public Licence."

This website is run by the U. S. National Institutes of Standards and Technology (NIST) (Building and Fire Research Laboratory; Indoor Air Quality and Ventilation Group), and it is the home of the CONTAM multizone model, which runs on the Windows and GNU/Linux platforms and can be downloaded for free.

The website aims to "...foster the development and facilitate the application of multizone ventilation and indoor environmental modeling in the areas of building design, operation, maintenance, investigation and research." "....[Y]ou will find software tools for performing multizone analysis, information on the applications of multizone modeling, multizone modeling case studies, and references to multizone modeling publications."

The R system is a Free Software programming environment for creating advanced applications in statistics, data analysis, simulation, and graphics. The system has add-on packages for graphical user interfaces, data bases, specialized plotting, and many other areas.