Vulnerability Assessment for Industrial Hazard

Building vulnerability for Industrial hazard was assessed for four different industrial hazards - Pool Fire, Vapour Cloud Explosion (VCE), Boiling Liquid Expanding Vapour Explosion (BLEVE) and Toxic Release Guwahati city.

Building Vulnerability for Pool Fire
A pool fire hazard vulnerability assessment for the detailed study areas was base on certain parameters, such as; building construction type characterized by the type of wall material and roof material. Weightages was assigned to different parameters/themes depending on the severity observed in the local conditions. The weightages of the themes were having value from 1 (low) to 10 (high), based on the construction material. Roof material was considered to be the most important parameter for the fire hazard because once a building is gutted by fire will easily spread to the neighbouring buildings if they have same type of roof material. Thus maximum weightage 10 was assigned to the roof material. Buildings materials (i.e. wall material) is another important parameter and thus assigned with the weightage of 3. It is also to mention here that other factors were not taken into account, such as space between individual buildings, or the distance to water bodies. The building vulnerability assessment in case of pool fire hazard was calculated. Based on the weightages and ranks for different parameters, buildings in the mapping unit were identified by a certain degree of vulnerability in terms of high, medium and low. The vulnerability value for pool fire ranges from 2 to 15. Based on this range vulnerability index was considered where value 2 to 4 represents low, 5 to 9 represents medium and 10 to 15 represents the high category.

Building Vulnerability for VCE
The building vulnerability assessment for the Vapour Cloud Explosion hazard was prepared based on certain parameters, such as; building material (wall material), roof material and number of stories of buildings. Weightages was assigned to different parameters/themes depending on the effect of vapour cloud explosion and severity observed in the local condition. Roof material was considered to be the most important parameter for vapour cloud explosion because the roof collapse might be one of the most direct effects of the explosion. Thus maximum weightage 10 was assigned to roof material. Building material, the next important parameter, was given weightage value of 6. The third important parameter taken into consideration was number of stories of a particular building. In case of an explosion event there is a chance of taller buildings will get much more effected which make leads to more vulnerable. Thus for vulnerability assessment of building this parameter was assigned to a weightage of 5. After calculating the total weight value, buildings were classified in a degree of vulnerability in terms of high, medium and low. For VCE the vulnerability value ranges from 2 to 13. The vulnerability index was prepared based on this range where value 2 to 3 represents low category, 4 to 9 represents medium category while 10-15 represents high category.

Building Vulnerability for BLEVE
Boiling Liquid Expanding Vapour Explosion is a consequence of explosion results from fireballs or from flame jets. Thus it is much more hazardous with respect to population as well as for buildings. For BLEVE, building vulnerability was assessed based on certain parameters, such as building construction type (wall material), roof material and number of stories. Weightages was assigned to different parameters depending on the severity observed in the local condition. The number of stories of a building is the prime important factor for the BLEVE hazard because if in between a building and the source of BLEVE a taller building would be there then it might be protect the smaller one though it depends on also the direction from which the BLEVE comes. Thus this parameter was assigned with a weightage of 10. Roof material and building material were assumed to be the next most important parameters because of their strength to withstand the explosion. Thus a weightage of 8 was assigned to both roof materials as well to building material.

Building Vulnerability for Toxic Release
Also an assessment was made for the vulnerability related to toxic release hazard based on the same parameters above mentioned. For toxic release hazard, the air tight condition of the building was considered to be the most important factor. In case of a toxic release event if the building is air tight then there will be less chance for people to inhale the toxic gas which is harmful for their health. Therefore, the maximum weightage 10 was assigned to the air tight condition of the building. But if a building is far away from the source of toxic release in that case there will be less probability for the people might be affected though the building is not at all air tight. However, this aspect will be taken into account in risk assessment, where the vulnerability and hazard factors are combined. The height of a building is also an important parameter for building vulnerability assessment in case of toxic release. Normally toxic gas is heavier than air. So it will float over the surface. So in toxic release event the short building are much more vulnerability than the tall buildings. Thus the number of stories was considered to the next important factor and assigned a weightage of 8. The air tight condition of a building mainly depends on roof material. These two parameters are thus assigned with a weightage of 2.