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

2. 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

3. Industrial Hazards
Fire
Explosion

4. 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

5. Gas Dispersion

6. 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

7. 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

8. Hydrogen Sulfide Limits
Ref:

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

10. 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

11. Tracer Gas Test - Result

12. What is a good SIP?

13. Wind is Bad! Makes Building Leaky

14. 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

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

16. Recommendations and Results

17. 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

18. Questions? Thank You