InDeVap Indoor Agent Dispersion Model
OptiMetrics developed the Indoor Evaporation (InDeVap) model for the U.S. Army Edgewood Chemical Biological Center (ECBC) to predict the effects of a hazardous chemical release in an enclosed ventilated space. InDeVap rapidly estimates the vapor concentration profile as a function of time for chemical warfare agents (CWAs) and hazardous chemicals released by liquid spill, spray, or explosive means. First Responders to such an incident could be exposed to hazardous vapors at high concentration levels. Estimating the vapor concentrations and hazard levels is extraordinarily complicated and uncertain. However, the potential range of concentrations that a Responder may face during such incidents can be estimated and predicted by the application of engineering models such as InDeVap.
Methodology
The InDeVap model includes the necessary logic, modeling, and methodology to account for the variables of interest for a terrorist incident. Among these variables are the:
- Type of Agent
- Quantity of Agent Released
- Method of Dissemination (Spill, Spray, or Explosive)
- Surface Area of Dispersed Liquid/Aerosol Fractions of the Payload Agent
- Air Exchange Rate Between Indoors and Outdoors
- Volume and Interior Surface Srea of the Rooms or Bbuilding
- Rrate of Convection to Other Areas/Zones of the Building
- Deposition Rate (Sorption) of Agent on Interior Surfaces
The computational estimates generated by the InDeVap model can be applied to the Hot Zone of an incident site to estimate the potential hazards in the enclosure. The model considers the:
- Physical Processes of Source Generation and Geometry
- Cloud Growth and Mixing
- Depletion and Loss Processes
- Natural Building Leakage
- Heating, Ventilating and Air-Conditioning Systems
- Collective Protection Air Purification Units
- Positive Pressure Ventilation
- Other Mitigation Devices/Techniques
Outputs
Hazardous vapor is generated during the dissemination process and through the evaporation of drops or pools. With InDeVap, the vapor concentration can be estimated with elapsed time until: the liquid pool has evaporated, the vapor concentration has reached zero, or some other predetermined maximum computation time has been reached. InDeVap’s outputs include estimates of the peak vapor concentration and graphical displays of the vapor concentration-time profile, along with the numerical results for the given conditions. Exercising the InDeVap model for an indoor Hot-Zone scenario provides a reasonable estimate of the potential hazards faced by occupants and the First Responders to the incident site.
Applications:
- Rapidly project potential hazard exposure levels in the Hot Zone and Warm Zone during terrorist and HAZMAT incidents involving toxic industrial chemicals (TICs) and CWA releases
- Provide estimates of potential hazard exposure levels to First Receivers at hospitals in the event of an incident and to support development of new protection requirements for those personnel
- Help determine Hot and Warm Zone protection requirements for First Responders at the scene of an incident
- Help incident response teams and medical personnel plan their overall response to hazardous events
