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Calcimator

Vapor Dispersion Calculator

Estimate downwind hazard distance using Gaussian plume dispersion modeling.

Inputs

Results

Hazard Distance (ft)

640

Hazard Distance (miles)

0.12

Hazard Distance (meters)195
Hazard Zone Area (acres)14.75
Vapor Density (Air=1)1.24
Heavier Than Air1
Travel Time (min)0.7
How to Use This Calculator
  1. Enter the Release Rate (lbs/min) from the incident report or estimate based on container size and breach type.
  2. Input the Wind Speed (mph) from on-site weather monitoring and select the Atmospheric Stability class (1=Very Unstable to 6=Very Stable).
  3. Enter the Molecular Weight (g/mol) for the released chemical — find this on the SDS or in NIOSH/CAMEO databases.
  4. Set the Target Concentration (ppm) to the ERPG-2 or AEGL-2 value for the chemical to define the protective action zone.
  5. Review Hazard Distance (ft) and Hazard Zone Area (acres) to establish protective action zones for evacuation or shelter-in-place.
  6. Check Vapor Density and Heavier Than Air to determine whether the vapor will accumulate in low-lying areas or dissipate upward.
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