Overview#
A chlorine gas release from a water treatment facility is reported at 14:37. By 14:40, the incident commander needs to know which streets to close, how far downwind to evacuate, and what concentration responders will encounter at the perimeter. There is no time to run spreadsheet calculations or wait for an environmental consultant. The Hazmat Dispersion Modelling module applies the Gaussian plume equation, the same mathematical foundation used in EPA reference tools, to the real-time weather conditions at the site and returns protective action zones in seconds.
The system is built for emergency responders, hazmat teams, and environmental crime investigators who need defensible, rapid plume estimates during active incidents, not after-action reports.
Open Standards#
- Pasquill-Gifford Atmospheric Stability Classification: The dispersion engine classifies atmospheric stability into classes A through F using the Turner method, then applies Briggs urban dispersion coefficients to drive the Gaussian plume equation for concentration calculations.
- EPA Acute Exposure Guideline Levels (AEGL): AEGL-1, AEGL-2, and AEGL-3 thresholds (60-minute values in both ppm and mg/m³) from the US EPA AEGL programme are used directly to define protective action zones and colour-coded contour polygons.
- GeoJSON (RFC 7946): All calculated plume contours and evacuation zone boundaries are output as GeoJSON Feature objects with Polygon geometries referenced to WGS-84, enabling direct consumption by mapping and geofence services.
- UN Model Regulations on the Transport of Dangerous Goods (UN Numbers): Each chemical in the hazmat database is keyed by its UN number (e.g. UN1017 for chlorine), providing responders with the internationally recognised identifier used on placards and shipping papers.
- UN Globally Harmonised System of Classification and Labelling of Chemicals (GHS): Chemical records store GHS pictogram codes, signal words, hazard statement (H) codes, and precautionary (P) codes, surfacing standardised hazard information alongside the dispersion model output.
- NFPA 704 (Standard System for the Identification of the Hazards of Materials for Emergency Response): Health, flammability, instability, and special-hazard ratings on the 0-4 NFPA Fire Diamond scale are stored per chemical and presented to responders entering the modelled zone.
- US DOT/PHMSA Emergency Response Guidebook (ERG): Isolation distances and initial action procedures from the ERG (2024 edition) are imported by guide number and surfaced alongside plume calculations to provide first responder guidance consistent with the national standard reference.
- OASIS Common Alerting Protocol (CAP) v1.2: Ingested weather alerts from NOAA NWS are parsed using CAP severity, urgency, and certainty classifications, and computed zone boundaries are fed to community notification systems via CAP-compatible messaging.
Last Reviewed: 2026-02-05 Last Updated: 2026-04-14
Key Features#
- Gaussian Plume Modelling: Industry-standard atmospheric dispersion calculations using source emission rates, wind speed and direction, atmospheric stability classification (Pasquill-Gifford), and effective release height
- Chemical Database: Comprehensive chemical properties database including health exposure limits (AEGL, ERPG, IDLH), molecular weights, vapour pressures, and toxicity data for hazard assessment
- Real-Time Weather Integration: Automatic ingestion of current wind speed, direction, atmospheric stability, temperature, and humidity from weather station feeds for accurate plume modelling
- Evacuation Zone Generation: Automated calculation of protective action zones including immediate danger areas, shelter-in-place zones, and downwind evacuation corridors based on AEGL concentration thresholds
- Multi-Source Modelling: Support for multiple simultaneous release sources with combined plume calculations for complex industrial scenarios involving several emission points
- Time-Varying Conditions: Model plume behaviour as wind conditions change, providing updated evacuation recommendations and concentration forecasts over time as the incident evolves
- Terrain Effects: Adjust dispersion calculations for terrain features, building wake effects, and surface roughness that influence real-world plume behaviour
- Responder Safety Perimeters: Calculate safe approach distances, required PPE levels, and decontamination zone locations based on modelled concentration levels
Use Cases#
- Industrial Chemical Release: Model chemical plumes from facility accidents to determine affected areas, calculate evacuation zones, and guide emergency response resource positioning
- Transportation Incidents: Assess hazardous materials releases from truck, rail, or pipeline incidents with rapid plume modelling to protect nearby communities
- Emergency Response Planning: Pre-plan response scenarios for high-risk facilities and transportation corridors with modelled plume footprints under various weather conditions
- Responder Protection: Calculate safe approach routes, required protective equipment, and decontamination requirements for first responders entering contaminated areas
- Community Notification: Generate geographic boundaries for public notification and evacuation orders based on modelled concentration levels and AEGL health exposure limits
Integration#
The module integrates with weather station feeds for real-time meteorological data, geospatial mapping for evacuation zone visualisation, PSAP notification systems for community alerting, and incident command tools for response coordination. Chemical database connects with EPA (CAMEO Chemicals) and NOAA reference data.