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
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Department of Chemical Engineering
University Teknology Malaysia
Y = k1 + k2 ln V
Here, te is the effective time duration (s), t is the time duration of pool burning (sec), Ie is the effective radiation intensity (W/m2), I is the radiation intensity from pool burning (W/m2), te is the effective time duration (s), po is peak overpressure (N/m2), J is impulse (Ns/m2), C is concentration (ppm) and T is time interval (min).
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
PEL, TLV etc designed for workers are overly conservative – designed for long-term exposure, not for short-term, emergency condition
AIHA: ERPG - Emergency Response Planning Guideline
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 publicToxic Effect Criteria
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.
… without experiencing or developing irreversible or other serious health effects or symptoms that could impair their ability to take protective action
… without experiencing or developing life threatening health effects (similar to EEGL)
Sometimes called TEEL
Example : Ammonia - ERPG 1,2,3 = 25,200,1000 ppmERPG (see pp201-202 Crowl & Louvar)
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 EEGLEEGL
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.IDLH
Toxic end points follows (in order of preference)
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.Toxic End Point