WHAT IS AN ACCIDENT

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WHAT IS AN ACCIDENT
CA57
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OBJECTIVE

• Identify types of potential chemical accidents
  and associated hazards

CA58
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AN ACCIDENT . . .

• Can be defined in several ways
• an unplanned release of chemical warfare agent
  into environment at levels which exceed those
  permitted by state or federal regulations
• more conservative definition is any unplanned
  event that could lead to the release of chemical
  warfare agent

CA59
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SIZE OF ACCIDENT

• Important to know amount of material accidentally
  released
• Amount of material released called source term
• Source term and weather conditions at time of
  release determine
• how far downwind hazardous materials will travel
• concentration of chemical warfare agent to which
  people could be exposed

CA60
5
PROXIMITY TO POTENTIAL ACCIDENT SITE

• Also important to know how close people might be
  to a potential accident site and their location
  with respect to airborne agent plume

Illustrated CSEPP installation and community
CA61
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ACCIDENT LIKELIHOOD

• Most likely accidents are small ones that do not
  pose a threat except to someone in very close
  proximity to accident
• Large accidents (source terms large enough to
  pose a threat to community) have much lower
  probability of occurring
• Unlikely that an accident will cause injury or
  death to anyone

CA62
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WHAT IS MEANT BY UNLIKELY?

• Engineers and scientists systematically studied
  different ways accidents could occur and
  estimated how likely events were that caused an
  accident
• They estimated probabilities of many different
  accidents and calculated number of fatalities
  that could occur for each accident
• They calculated the consequences of each accident

Calculation of risk
CA63
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POTENTIAL ACCIDENT TYPES AND HAZARDS

• If accident large enough to pose threat to
  public, dominant hazard is from breathing air in
  which agent exists as vapor
• Paths for liquid chemical warfare agent to travel
  from accident to off-site are limited and
  relatively easy to block therefore people
  off-site unlikely to encounter liquid agent

CA64
9
THREE BASIC TYPESOF POTENTIAL ACCIDENTS

• 1. Spill
• 2. Explosion
• 3. Fire

CA65
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SPILL

• Onto ground or other surfaces
• Resulting puddle of agent (liquid deposition) can
  evaporate into vapor and drift downwind

(not to scale)
Example of a plume resulting from a spill
CA66
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EXPLOSION

• Causes droplets of agent to be formed
• Larger, heavier droplets quickly fall to ground
  (deposition)
• Releases vapors and aerosols (smaller droplets
  and particles) that can travel greater distances

Example of a plume resulting from an explosion
(not to scale)
CA67
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FIRE

• Both aerosols and vapors are formed
• Vapors and aerosols lifted higher into air
  because of heat from fire
• Hazard similar to those of an explosion

Example of a plume resulting from a fire
(not to scale)
CA68
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DIFFERENCE BETWEENAEROSOLS AND VAPORS

• Think of a chemical agent release in terms of
  hair spray coming from a spray can
• when spray is release, it is an aerosol
• larger particles and/or droplets are deposited
  near point of release
• particles quickly fall out of air onto hair and
  skin
• person across room can smell hair spray from
  breathing vapors released

CA69
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WHAT IF AN ACCIDENT OCCURS?

• It is very unlikely the public would be exposed
  to droplets and aerosols
• Particles will mostly fall out of plume (via
  deposition) by time plume reaches installation
  boundary

CA70
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VAPOR HAZARD

• For most accidents, the primary health hazard
  comes from vapors when they are breathed in or
  come in contact with skin or eyes
• Agent vapors pose greatest hazard when inhaled
  because they are rapidly absorbed by lung tissues
• Lethal dosage for agent vapor breathed in is
  several times lower than lethal dosage for vapor
  contact with skin

CA71
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ACCIDENT CATEGORIES

• Selection of protective action strategies
  contingent on characteristics of accident
• Accident categories are group of accident
  scenarios bound together by common source terms
  and meteorological conditions
• Designed to support grouping of large number of
  protective action strategies
• Each installation has set of accident categories

CA72
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CHEMICAL EVENT EMERGENCYNOTIFICATION SYSTEM

• Standard chemical accident notification
• Provides a common language between installation
  and off-site emergency responders
• Fosters clear understanding and ready reference
  for emergency response actions
• Off-site response consists of 4 levels
• nonsurety (does not involve chemical warfare
  agents)
• limited area, post-only, and community
  emergencies (involve chemical warfare agents)

CA73
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NON-SURETY EMERGENCY

• General interest to public
• Poses no chemical surety hazard
• Action Notification to IRZ designated points of
  contact

Army Installation Boundary
Limited Area Boundary
Illustrated CSEPP installation and community
CA74
19
LIMITED AREA EMERGENCY

• Declared when predicted chemical agent no-effects
  dosage does not extend beyond chemical limited
  area
• Action Notification of IRZ and State
  points-of-contact
• IRZ emergency response officials may go to level
  of readiness

Army Installation Boundary
Limited Area Boundary
Plume
Illustrated CSEPP installation and community
CA75
20
POST-ONLY EMERGENCY

• Declared when predicted chemical agent no-effects
  dosage extends beyond chemical limited boundary
  but not installation boundary
• Not expected to present danger to off-site public
• Action Notification of IRZ, PAZ, and
  State-designated points-of-contact
• IRZ response organizations mobilize
• precautionary protective actions may be
  initiated in nearby areas

Army Installation Boundary
Limited Area Boundary
Plume
Illustrated CSEPP installation and community
CA76
21
COMMUNITY EMERGENCY

• Declared when predicted chemical agent no-effects
  dosage extends beyond installation boundary
• Action Notification of IRZ, PAZ, and
  State-designated points-of-contact
• all emergency responseorganizations mobilize
• IRZ and affected PAZ areasimplement specified
  protective actions

Army Installation Boundary
Limited Area Boundary
Plume
Illustrated CSEPP installation and community
CA77
22
CHEMICAL WARFAREAGENT DETECTION

• Armys detection capability consists of low-level
  and gross-level detectors
• Any vapor detection efforts off-site would be
  conducted by Army survey teams using appropriate
  equipment

CA78