Fire Impact to Personnel, Structures, and Equipment

Once the fire characteristics are calculated, an assessment of the impact of the fire needs to be completed. Fires produce four major outputs gases, flame, heat, and smoke. The materials involved in the fire will determine the combination of these four outputs. For example, crude oil will produce a very dark thick smoke cloud, and ethylene does not produce much smoke, but does have a very large flame. 

The outputs can create consequences to personnel, structures, and equipment. There are different approaches for assessing consequences. Criteria can be developed that will allow the analyst to compare the results of the calculations to predetermined criteria. The results either meet or exceed the criteria. These criteria can be established based on a conservative approach of assuming a steady-state condition. Another approach is the use of more sophisticated heat transfer techniques, where a time-dependent onset of critical criteria is modeled. 

Data and procedures presented in this section can be used in either approach. Time-independent approximations of failure criteria are presented to provide first-order estimates of fire consequences. Time-dependent criteria are also presented where specific scenarios warrant more detailed analysis. Most of the thermal criteria is presented in terms of heat flux, although some temperature criteria are also presented. A conservative methodology is presented to translate heat flux from a fire to surface temperature on a material target. 

When there is a line-of-sight between a person and the flame, the main impact is thermal radiation. The primary potential effects of thermal radiation are  

The time to damage human skin increases logarithmically with the increase in skin temperature. Skin damage begins at about 45°C (113°F) and becomes virtually instantaneous at 72°C (162°F). Complex methods involving the use of thermal skin property are detailed in the literature (SFPE, 2000). 

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