NIST Multizone Modeling Website
Species and Contaminants
Airborne contaminants are dispersed throughout buildings due to several different transport mechanisms. These include air movements into, out of, and within a building system; heating, ventilating, and air-conditioning (HVAC) systems; removal by filtration, deposition, and sorption; generation; chemical reaction; and radio-chemical decay. CONTAM provides you with the ability to simulate these methods of dispersal of airborne contaminants within built structures.
Species is a general term used (by CONTAM) to identify substances that can be used as contaminants during a simulation, i.e., contaminants are those species you designate to be used in a simulation. You can include as many species/contaminants as you need within a project.
CONTAM handles both trace and non-trace contaminants. Trace contaminants are those that exist at concentrations that do not cause a "significant" change in the density of air. Non-trace contaminants are those that can affect the density of the air. The mass fractions of non-trace contaminants will always sum to 1 kg/kg, i.e., they are the constituents of the air. Typically, you might want to treat water vapor as a non-trace contaminant.
In versions prior to CONTAM 2.4 an underlying assumption of the model was that each zone is considered to have a single concentration value at any given time. This assumption is sometimes referred to as the "well-mixed" zone assumption. With respect to contaminant analysis, this means that there are no spatial concentration gradients within a given zone. However, beginning with version 2.4, zones can be preconfigured by the user to be 1 dimensional convection/diffusion zones in which contaminants can be allowed to vary along a user-defined axis.
