Shelter in Place Design for Toxic and Flammable Hazards: Case Study Anay P. Raibagkar 2017 CSCE Annual Conference

Key Items Industrial Hazards Shelter in Place (SIP) Dispersion Modeling: Dispersion of Toxic Cloud Building Leak Tightness: Tracer Gas Test Occupant vulnerability from Toxic Hazards Recommendations

Industrial Hazards Fire Explosion

Bhopal Disaster Largest Industrial accident in the history Over 500,000 people were exposed to methyl isocyanate (MIC) The official immediate death toll was 2,259 Occurred on the night of 2–3 December 1984 at the Union Carbide India Limited (UCIL) pesticide plant in Bhopal

Gas Dispersion

Case Study SIP: Control Room Building Toxic Hazards: Hydrogen Sulfide The control room building must be able to provide a safe shelter for at least 60-mins in case of a toxic release Toxic Hazards: Hydrogen Sulfide Evaluate building’s leak tightness – Tracer Gas Testing Calculate toxic concentration inside the building from dispersion results and leak tightness Provide recommendations on leak tightness

Building: Shelter In Place Key Issues Multiple toxic release locations (one or more types of toxics) Several possible wind directions with different probabilities Angle of Release: Several Possibilities Building has different leakage characteristics at different wind speeds CFD techniques can be used but input data is difficult Toxic Release 2 Toxic Release 1 Building: Shelter In Place Toxic Release 3

Hydrogen Sulfide Limits Ref: http://enviromed.ca/index.php?id_cms=26&controller=cms

Dispersion Modeling Toxic Cloud Building Dispersion modeling must consider Different weather conditions and wind speeds Potential release sources

Tracer Gas Test Tracer gas test is used to determine building’s leak tightness Leak Tightness is typically defined in terms of Air Changes Per Hour (ACH) 1 ACH means building will replace its entire volume of air in one hour with air leaking from outside Test involves the release of Carbon Dioxide into the building and observe the decay of its concentration over time

Tracer Gas Test - Result

What is a good SIP?

Wind is Bad! Makes Building Leaky

Toxic Concentration Calculation Toxic concentration inside the building is a function of - External concentration (obtained from dispersion modeling) - ACH from tracer gas test -Assume perfect and instantaneous mixing (uniform

Recommendations and Results Relationship between infiltration rate and duration for which the SIP can be considered “safe”

Recommendations and Results

Conclusions Effectiveness of a building envelope against toxic hazards is critical in designing a good shelter in place building Design must rely on dispersion modeling under various weather conditions Building’s leak tightness must be evaluated on a case by case basis After retrofits have been installed, ACH should be confirmed with another test

Questions? Thank You