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WHAT IS AN ACCIDENT

WHAT IS AN ACCIDENT. CA57. OBJECTIVE. Identify types of potential chemical accidents and associated hazards. CA58. AN ACCIDENT . . . Can be defined in several ways

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WHAT IS AN ACCIDENT

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  1. WHAT IS AN ACCIDENT CA57

  2. OBJECTIVE • Identify types of potential chemical accidents and associated hazards CA58

  3. 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

  4. 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

  6. 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

  7. Risk = Probability For of X Consequences ∑ all Accident (Times)(Summed) Events 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

  8. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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 • Army’s 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

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