Source terms

The ability of any model to predict indoor air pollutant concentrations depends on the accuracy of the source models incorporated into the model. RISK uses source models developed as a part of EPA's source characterization research program and source models provided in the literature. The model incorporates a wide range of emission characteristics to allow simulation of the range of sources encountered in indoor spaces. Several sources are allowed in each room.

The model includes a database of source emission rates for these various sources based on research conducted by the Indoor Environment Management Branch, National Risk Management Research Laboratory of EPA. The user can override the database emission rates.

Generally sources can be divided into the following categories:

Source behavior can be described by empirical source models or by source models based on mass transfer theory. The constants developed for empirical models are often affected by test conditions. For example, if gas-phase mass transfer limits the mass transfer rate, the empirical constants are affected by the air speed over the source. In general models based on mass transfer theory are easier to scale to new situations than are empirical models. RISK allows the user to use both types of source models. See references 7 and 8 for details of the mass transfer models.

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