Consequence Analysis Dr. AA Department of Chemical Engineering University Teknology Malaysia

Consequence Analysis Determine the amount / rate of release –Source modelling Model the dispersion Effect of Chemicals released –Toxic Effect –Fire –Explosion Estimate Fatality : Probit Estimate injury / health effect –Heat Effect / Toxic Effect Estimate Losses Hazard Modelling

Estimation of Fatality (Probit Analysis)

Estimation of Fatality: Probit Analysis The dose level of the various hazard events against fatality can be conveniently determined using Probit Analysis. It is a graphical and Look-up Table approach to determine probability of fatality 4

Probit Analysis The probit variable Y is computed from: Y = k 1 + k 2 ln V Values of constants k 1, k 2 and causative variable V (representing the dose) are given in table Once the probit is obtained, it can be converted into % fatality 5

Probit: Toxic Release 6 Causative variable, V =  C a T (C is concentration in ppm, T is time in minutes) Probit Parameters Type of InjuryaK1K2 Ammonia Death Carbon Monoxide Death Chlorine Death Ethylene Oxide Death Hydrogen Chloride Death Nitrogen Dioxide Death Phosgene Death Propylene Oxide Death Sulfur Dioxide Death Toluene

Probit: Fire and Explosion Type of injury or damage Causative variable (V) Probit parameters k1k1 k2k2 Fire Burn deaths from flash fire Burn deaths from pool burning Explosion Deaths from lung haemorrhage Eardrum ruptures Deaths from impact Injuries from impact Injuries from flying fragments Structural damages Glass breakage popoJJJp0p0popoJJJp0p Here, t e is the effective time duration (s), t is the time duration of pool burning (sec), I e is the effective radiation intensity (W/m 2 ), I is the radiation intensity from pool burning (W/m 2 ), t e is the effective time duration (s), p o is peak overpressure (N/m 2 ), J is impulse (Ns/m 2 ), C is concentration (ppm) and T is time interval (min).

Conversion of Probit to Fatality data 8 % %

Heat Effect Criteria

Thermal Burn Injury Criteria (FEMA, 1990) Radiation Intensity Time for severe pain (sec) Time for second degree burn (sec)

Permissible Thermal Radiation Exposure for Flares from API 521 (1997) Thermal Radiation Intensity (kW/m 2 ) Type of Damage 1.6Permissible level at any location where some personnel are continuously exposed 4.7Permissible level in areas where emergency actions lasting several minutes may be required by personnel without shielding but with appropriate clothing 6.3Permissible level in areas where emergency actions lasting up to 1 minute may be required by personnel without shielding but with appropriate clothing 9.5Permissible level in areas where exposure to personnel is limited to a few seconds, sufficient for escape only

Thermal Dose for exposure to fireball Thermal Dose (kJ/m 2 ) Type of Injury 40Threshold of pain 100Sunburn (first degree burn) 150Blisters (Second-degree burn) 2501 % fatal (third degree burn) % fatal (third degree burn) % fatal (third degree burn)

Effect of Thermal Radiation on Structures TNO, 1992 Type of DamageDamage Level 1 (radiation intensity, kW/m 2 ) Damage Level 2 (radiation intensity, kW/m 2 ) Steel10025 Wood152 Synthetic Materials 152 Glass4- Damage Level 1 – Surfaces of exposed materials catch fire and structural elements collapse or rupture Damage Level 2 - Surfaces of exposed experience serious decoloration as well as peeling and structural elements undergo substantial deformation

Thermal Radiation Limits on Structure (Lees, 1996) Radiation intensity (kW/m 2 ) Limit Description (BS5908, 1990) 37.5Intensity at which damage is caused to process equipment 25Intensity at which nonpiloted ignition of wood occurs 12.5Intensity at which piloted ignition of wood occurs Radiation intensity (kW/m 2 ) Limit Description (Design Guidance by Dinneno, 1982) 30Spontaneous ignition of wood 20Ignition of No 2 fuel oil in 40 seconds 10Ignition of No 2 fuel oil in 120 second 18-20Cable insulation degrades 12Plastic melts 37.5Equipment damage 9Equip. damage (conservative value used in flare design)

Toxic Effect Criteria

What Concentration are considered dangerous? –PEL, TLV etc designed for workers are overly conservative – designed for long-term exposure, not for short-term, emergency condition Some guidelines –AIHA: ERPG - Emergency Response Planning Guideline –NIOSH: IDLH –Nat Acad Sci : EEGL (emergency exposure guidance level) and SPGEL(short term public emergency guidane) –TLV, PEL etc For design of ERP, the ERPG, SPEGL, EEGL are more directly relevant for general public

ERPG (see pp Crowl & Louvar) ERPG-1 –Max airborne concentration below which it is believed nearly all individuals could be exposed for up to 1 hour without experiencing effect other than mild transient adverse health effect or perceiving a clearly defined objectionable odor. ERPG-2 –… without experiencing or developing irreversible or other serious health effects or symptoms that could impair their ability to take protective action ERPG-3 –… without experiencing or developing life threatening health effects (similar to EEGL) Sometimes called TEEL –Example : Ammonia - ERPG 1,2,3 = 25,200,1000 ppm

ERPG (Selected Chemicals) ChemicalERPG1 (ppm)ERPG2 (ppm)ERPG3 (ppm) Acrylic Acid Ammonia Benzene Chlorine1320 Formaldehyde11025 Methanol Methyl Isocyanate Phenol Styrene Sulfur dioxide Toluene Vinyl acetate575500

EEGL EEGL – Emergency Exposure Guidance Level –Defined as concentration of gas, vapour aerosol that is judged acceptable and that allows exposed individuals to perform specific tasks during emergency condition lasting from 1 to 24 hours. National Research Council committee on Toxicology (USA) has submitted EEGL for 44 chemicals. NERC also developed SPEGL (Shor term public emergency guidance) –Defined as acceptable concentration for exposure for members of general public –Generally SPGEL is 10-50% of EEGL

SOME EEGL Chemicals1 hour EEGL24 hour EEGL Acetone Ammonia100 Benzene10.1 Carbon Monoxide40050 Chlorine30.5 Chloroform10030 Methane5000 Methanol20010 Nitrogen dioxide1 (SPEGL)0.04 (SPEGL) Sulfur dioxide105 Xylene200100

IDLH IDLH by NIOSH Concentration for acute toxicitymeasures for common industrial gas Defined as a condition “ that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effect or prevent escape from such an environment”. Considered as a maximum concentration above which only a highly reliable breathing apparatus providing maximum protection is permitted.

Toxic End Point EPA promulgamated a set of toxic end points to be used for air dispersion modeling for toxic gas releases as part of EPA RMP Toxic end points follows (in order of preference) –ERPG-2 –LOC (level of concern) - the maximum concentration of an extremely hazardous substance in air that will not cause serious irreversible health effects in the general population when exposed to the substance for relatively short period.

Recommended Hierarchy of alternative concentration guidelines Primary Guideline Hierarchy of alternative guidelines Source ERPG1 EEGL (30 minute) IDLH AIHA NRC NIOSH ERPG2 EEGL (60 minutes) LOC PEL-C TLV-C 5 X TLV-TWA AIHA NRC EPA/FEMA/DOT OSHA ACGIH ERPG3 PEL-STEL TLV-STEL 3 X TLV-TWA AIHA OSHA ACGIH