Software Description
The Indoor model is a dynamic fugacity-based model that generates time-dependent concentrations of contaminants in a defined indoor environment such as a house. The model allows for up to three rooms, one of which may be a bathroom. Each room consists of four compartments, namely air, wallboard, and soft and hard surfaces. If a bathroom is defined, the additional compartment of water is included. Chemical emissions may be constant or a pulse to any compartment in any room or any combination of compartments and rooms.
This model has been designed to be loosely coupled to a human model such as the PBPK model that is a physiologically-based pharmacokinetic fugacity model of a human that calculates time-dependent concentrations of the chemical in blood and five tissue groups (liver, fat, skin, and richly and slowly perfused tissue). The PBPK model accepts inputs from ingested food and water, an external dermal exposure medium, and respired air. The respired air in the PBPK model accepts the time-dependent concentrations generated by the Indoor model. Either model may also be used on its own.
This model is useful for estimating the concentrations that may be experienced as a result of the introduction of chemical substances by a variety of routes including the surface application of cleaning products, chemical presence in drinking water, in consumer products such as solvents, fragrances and pesticides, and by infiltration from outside sources. Additional information can be obtained on the residence time or persistence of the substance in the indoor environment, the primary compartments of accumulation and the most significant degradation and loss processes. The user can explore the sensitivity of the desired results to variation in input parameters by incremental adjustment of these parameters on a one-by-one or combined basis.
Features of the Indoor model:
- Provides a database of chemicals and chemical properties that may be added to or modified by the user.
- Provides a database of houses and house properties that may be added to or modified by the user.
- Provides context-sensitive Help.
- Allows on-screen display of the model results (including inputs).
- Provides an on-screen diagram of chemical movement into, out of and within the house.
- Provides on-screen time course charts of chemical fugacity, concentration and amounts.
- Displays and prints the model calculations, as performed by the program.
- Allows the program results to be saved as a comma separated (csv) text file viewable by most standard spreadsheet software for subsequent analysis or graphing.
This program was based on the following publication:
Webster, E.M., Qian, H., Mackay, D., Christensen, R.D., Zaleski, R. 2014. A dynamic indoor contaminant model for assessing human exposure to volatile organic chemicals. Prepared for submission to Environ. Sci. Technol.
The required input data are:
Chemical Properties
- Chemical name
- Molar mass and molar volume
- Data temperature
- For Type 1 chemicals, partitioning properties as either:
- The log (octanol - air partition coefficient), log Koa and air-water partition coefficient, Kaw, or
- The log (octanol - water partition coefficient), log Kow and air-water partition coefficient, Kaw
- The Kaw may be defined as either
- Kaw, or
- Henry's Law Constant, or
- water solubility, vapour pressure and melting point
- degradation half-lives in air, aerosols or dust, soft surfaces, hard surfaces, and wallboard
House Properties
- House name
- Number of rooms (maximum of three)
- First room may be identified as a Bathroom
For each room
- Floor area, ceiling height
- Air exchange with air circulator (either furnace or air conditioner), air exchange with outdoors
- Three types of surfaces are defined: soft and hard surfaces and wallboard.
Surface Properties
- Area and thickness of quasi-liquid layer on each surface type
- Dust area and loading on soft and hard surfaces (Wallboard is assumed to be free of surface dust.)
Shared Properties
- Mass transfer coefficients to air boundary layer, to film on each surface type
- Temperature
- Volume fraction of particulate in air
- Densities of particulate and of each surface type
Initial Concentrations
For each room separately, the concentration of chemical in air, quasi-liquid layer on each surface type
Emissions
- For each compartment of each room, either no emission, a constant emission or a pulse emission
If room 1 is a bathroom then a water-type emission is defined as
- No emission, shower or bath
- Transfer efficiency for the selected chemical and selected water use
- Start and duration time
- Concentration in the water
- Total volume of water used
Simulation Times
- Total simulation time
- Time step
Model output includes
- All input parameters including chemical and house properties, initial concentrations in the house, the emissions and all parameters derived from these inputs
- The concentration, fugacity, fugacity capacity (Z), and amount of chemical in each compartment of each room
- The chemical fluxes and D values
- A diagram of chemical movement
- Time course charts of fugacity, concentration and amount
Please read the software license before downloading the software. Use of the software constitutes your agreement to abide by the terms and conditions set out in the license agreement.