Figures (7)  Tables (5)
    • Figure 1. 

      Analysis of hazardous chemical accidents and their outcomes.

    • Figure 2. 

      HEGADAS model plume shape in the ideal state [37].

    • Figure 3. 

      Triangular, square and hexagonal cellular space.

    • Figure 4. 

      Cellular automaton state update process.

    • Figure 5. 

      Flow chart of smoke identification based on computer vision.

    • Figure 6. 

      Smoke recognition using computer vision.

    • Figure 7. 

      Future research directions

    • TimeAccidentConsequences of the accident
      2014.01.01Hydrogen sulfide poisoning accident of Shandong Binhua Bingyang Combustion Chemical Co., Ltd, in ChinaIt caused a poisoning accident, resulting in 4 deaths, 3 injuries and direct economic loss of 5.36 million RMB
      2015.12.17Sulfur dioxide leakage accident of Excel Industries in IndiaIt caused 1 death and 4 people were poisoned and resuscitated
      2016.01.09Hydrogen fluoride leakage poisoning accident of Weifang Changxing Chemical Co., Ltd, in ChinaIt caused a poisoning accident, resulting in 3 deaths and 1 injury
      2016.06.27Explosion accident of pascagula gas plant in Mississippi, USASurrounding residents were evacuated and the gas plant was closed for more than 6 months
      2017.05.13Chlorine gas leakage poisoning accident of Lixing Special Rubber Co., Ltd, in ChinaIt resulted in 2 deaths and 25 hospital admissions
      2017.08.31Chemical plant explosion in Texas, USAIt resulted in the poisoning of 21 people and the evacuation of residents within a 1.5-mile radius of the accident site
      2018.11.28Vinyl chloride leakage and deflagration accident of Shenghua chemical company of China National Chemical Corporation in ChinaIt left 24 people dead and 21 injured
      2019.04.02Isobutylene leakage explosion at KMCO chemical plant in Crosby, Texas, USA.It resulted in 1 death, 2 people were seriously burned and at least 30 other workers were injured to varying degrees
      2019.04.15Poisoning accident of Qilu Tianhe Huishi Pharmaceutical Co., Ltd. in ChinaIt caused 10 deaths and 12 injuries, resulting in direct economic losses of 18.67 million RMB
      2019.06.21Fluorinated acid alkylation unit explosion at Philadelphia energy solutions corporation refinery in USASmoke from the explosion covered much of downtown Philadelphia and South Philadelphia, causing minor injuries to 5 people
      2020.05.07Styrene leakage accident at LG Polymers Ltd. in IndiaIt caused 13 deaths and more than 5,000 people felt unwell to varying degrees
      2021.04.21Poisoning accident of Heilongjiang Kelunda Technology Co., Ltd., in ChinaIt resulted in 4 deaths and 6 toxic reactions

      Table 1. 

      Typical atmospheric dispersion events of accidental release.

    • ParametersExperiment
      BurroCoyoteDesert
      Tortoise
      GoldfishMaplin
      Sands
      Thorney
      Island
      Thorney
      Island
      Fladis
      Number of experiments8343129216
      Test mediumLNGLNGNH3HFLNGFreon/N2Freon/N2NH3
      Leakage sourceBoiling point heavy gasesBoiling point heavy gasesTwo-phase heavy gasesTwo-phase heavy gasesBoiling point heavy gasesHeavy gasesHeavy gasesTwo-phase heavy gases
      Total amount of release (t)10.7−17.36.5−12.710−36.835−381−6.63.15−8.74.80.036−1.2
      Release time (s)79−19065−98126−381125−36060−360Momentay460180−2,400
      Release surfaceWaterWaterSandy soilSandy soilWaterSandy soilSandy soilSandy soil
      Surface roughness0.00020.00020.0030.0030.00030.005−0.0180.005−0.0180.01
      Atmospheric stabilityC−EC−DD−EDDD−FD−FE−F
      Farthest distance (m)140−800300−400803,000460−650500−800500−800240
      Year of experiment19821983198519871984198519851993−1996

      Table 2. 

      Famous foreign experiments on diffusion of toxic gases[20].

    • Surface wind
      speed (m/s)
      Daytime sunshineNighttime conditions
      StrongModerateSlightThinly overcast or
      > 4/8 low cloud
      < 3/8 cloud
      < 2AA–BBFF
      2–3A–BBCEF
      3–4BB–CCDE
      4–6CC–DDDD
      > 6CDDDD

      Table 3. 

      Atmospheric stability levels using the Pasquill-Gifford diffusion model [34,35].

    • Pasquill-Gifford
      stability rating
      $ {\mathit{\sigma }}_{\mathit{y}} $/m$ {\mathit{\sigma }}_{\mathit{z}} $/m
      Rural conditions
      A0.22x(1 + 0.0001x)−1/20.20x
      B0.16x(1 + 0.0001x)−1/20.12x
      C0.11x(1 + 0.0001x)−1/20.08x(1 + 0.0002x)−1/2
      D0.08x(1 + 0.0001x)−1/20.06x(1 + 0.0015x)−1/2
      E0.06x(1 + 0.0001x)−1/20.03x(1 + 0.0003x)−1/2
      F0.04x(1 + 0.0001x)−1/20.016x(1 + 0.0003x)−1/2
      City conditions
      A–B0.32x(1 + 0.0004x)−1/20.24x(1 + 0.0001x)−1/2
      C0.22x(1 + 0.0004x)−1/20.02x
      D0.16x(1 + 0.0004x)−1/20.14x(1 + 0.0003x)−1/2
      E–F0.11x(1 + 0.0004x)−1/20.08x(1 + 0.0015x)−1/2
      Note: A–F are as defined in Table 3.

      Table 4. 

      Recommended Pasquill-Gifford model diffusion coefficient equation for plume dispersion (downwind distance x in m).

    • Model
      name
      Applicable conditionsScope of applicationCalculation accuracyRelevant parametersBasic principleApplicable conditionsAdvantages & disadvantages
      Gaussian modelNeutralLarge scale and short durationPoorDensity, explosion limit, temperature, wind speed, wind direction, atmospheric stability levelContinuous InstantaneousOne of the most widely used models, simple calculation, only applicable to neutral gas, poor simulation accuracy
      Sutton modelNeutralLarge scale and long durationPoorCy, Cz (diffusion parameters related to meteorological conditions)Similar distributionContinuous InstantaneousLarge errors when simulating the diffusion of combustible gas leakage
      P-G modelNeutralUnrestrictedPoorWind speed,
      atmospheric stability,
      topography, height of the leakage source,
      in itial state and nature of the substance
      Continuous InstantaneousMore human factors in determining atmospheric stability cause large deviations in diffusion simulation results
      BM modelMedium or heavyLarge scale and long durationAverageAverage concentration, initial concentration on gas cloud cross sectionStatistical analysis based on experimental dataContinuous, transient surface and body sourcesEasy to use, graphing by experimental data, not suitable for areas with large surface roughness, poor extensibility
      Box and similar modelsMedium or heavyUnrestrictedBetterMean cloud radius,
      mean cloud altitude,
      mean cloud temperature
      Consider the heavy gas as a cylinder according to the phenomenon of heavy gas sinkingMomentaryThe existence of discontinuous surfaces, simple calculations, large errors and large uncertainties
      Shallow
      layer
      models
      HeavyUnrestrictedBetterCloud density,
      cloud thickness,
      cloud velocity,
      ambient air density
      Shallow water equationContinuousHigh accuracy than box model, can simulate general complex terrain

      Table 5. 

      Comparison of empirical and simplified models[5].