A Risk-Based Approach for Selecting Fire Safety Alternatives for Life Safety
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A Risk-Based Approach for Selecting Fire Safety Alternatives for Life Safety

By Dr. IJsbrand van Straalen

TNO, the Netherlands

 

Introduction

The demand for a risk-informed, performance-based approach to fire safety in the Netherlands is growing. Various major incidents have emphasized the need to upgrade fire safety regulations. All major stakeholders involved have noted that the existing regulations are limited and that a risk-based approach should be developed.

The discussions about the implementation of such an approach show that fire safety engineers mainly think in terms of fire safety solutions. They know how solutions perform in relation to each other in terms of qualitative risks, but they have difficulty with determining how a given solution performs in terms of a given quantitative risk criterion. To tackle this discrepancy, Van Straalen (2014) [1] has developed a framework that relates well-defined risk criteria with generally applied fire safety solutions.

 

Framework for Life Safety

The framework as developed is based on the hierarchy promoted by the Inter-jurisdictional Regulatory Collaboration Committee (www.ircc.info). Through functional statements and operative requirements, which are quantified by actual risk criteria, the IRCC links the “Life Safety” goal to matching verification methods. The framework is shown below.

 

The framework starts with the definition of risk criteria for fire safety by translating relevant operative requirements for life safety. The next step pays special attention to the quantification of these risk criteria by accommodating perceptions of risk. To verify a required probability, underpinning scenarios have to be fitted with fire safety engineering tools by using a probabilistic approach. Such analyses will result in a calculated probability that an unwanted event will occur, and that value can be compared directly to the required risk criterion.

 

Example of a Long-Term Healthcare Facility

To show how the proposed risk-based approach applies to selecting fire safety alternatives for life safety, Van Straalen, et al. [2], made a detailed study to implement the framework. In this study, examples for two different healthcare facilities have been worked out for various fire safety solutions. One of the examples considers one fire compartment (indicated by the red lines) with 11 sleeping rooms, as shown in the building plan below. The compartmentalization of sleeping rooms according to the Dutch Building Decree is indicated by the green lines.

 

As a starting point, the target risk-value has been defined as the individual risk to one person. Based on accepted targets in other safety domains, this target has been set at a value of <1.0·10-5 probability of death per year. This value is in line with fire statistics in the Netherlands, which show that this value is of the same order of magnitude. It is noted that this risk-value represents all four risk criteria shown in the diagram above.

This example assumes that the patients in the facility need support from the staff of the healthcare organization to be evacuated out of the fire compartment to a safe part of the building. This example considers two situations: (1) application of passive fire safety measures according to the requirements of the Dutch Building Decree and (2) application of a sprinkler installation as an active fire safety measure.

Various scenarios have been considered and, through application of event trees and Monte Carlo simulations, the matching probabilities of individual risk have been determined. The graph below provides some results. The passive fire measures are according to the Dutch Building Decree. It also considers the case that every sleeping room is one fire compartment. Finally, it shows the scenario with a sprinkler system.


The results of those analyses show the following trends:

  • With passive fire measures, according to the Dutch Building Decree, at least eight staff are necessary to evacuate patients from the fire compartment. In this case, the probability of death is approximately 1.5·10-5. To reach the proposed target of <1.0·10-5, every sleeping room has to be a fire compartment.
  • With a sprinkler installation as an active fire measure in combination with two staff available to evacuate patients, the probability of death is approximately 0.4·10-5. This value meets the target that was set.

This example shows that it is possible to evaluate fire safety alternatives applying the developed risk-based approach, which makes use of a target for individual risk of death and probabilistic techniques.

As a result of this project, Van Straalen, et al. (2015b) [3], also presented a building model, which contains both a code-checking module for fire compartments and evacuation routes, and a module for the risk-based approach that has been developed.

 

 

References
[1] Straalen, IJ.J. van (2014). “Development of Risk-Informed Performance-Based Fire Safety Approach,” 10th International Conference on Performance-Based Codes and Fire Safety Design Methods, SFPE, Australia.

[2] Straalen, IJ.J. van, Gallis, H.R., Bezemer, R.A. (2015a). “Risk-Informed Fire Safety for Long-term Health Care Facilities – Explanation of a Decision Support System,” TNO-report 2015 R11060, 2015 (in Dutch) .

[3] Straalen, IJ.J. van, Gallis, H.R., Bezemer, R.A. (2015b). “Code Checking Fire Safety Long-Term Health Care Facility,” youtube movie, http://youtu.be/AWWGMmKLN8g.

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