Fire-fighting engineering services: methodology

Fire-fighting engineering services: methodology

One of the most important aspects of fire-fighting safety engineering concerns the application of methodological principles to define solutions suitable for the achieving design targets through quantitative analysis.

Our engineering company works in fire safety engineering services according to the “Methodology for fire-fighting safety engineering” of the Fire Prevention Code, which describes in detail the design methodology of fire safety engineering or fire-fighting performance design.

The Code lays down the following definitions

Fire safety engineering (performance method, fire safety engineering - FSE)
Application of engineering principles, rules and expert judgement based on scientific evaluation of the phenomenon of combustion, effects of fire and human behaviour, aimed at the protection of human life, at the protection of property and the environment, at the quantification of the fire risk and their effects and at the analytical evaluation of the optimal fire-fighting protection measures necessary to limit the consequences of the fire to predetermined levels.

Fire scenario
Complete and unique description of the fire evolution in relation to its three fundamental aspects: fireplace, activity and occupants.

ASET (available safe escape time)
The period of time calculated between the start of the fire and the time when the environmental conditions in the activity become such as to make the occupants unable to escape to or from a safe place.

RSET (required safe escape time)
Period of time calculated between the start of the fire and the moment when the occupants of the activity reach a safe place.

PTAT (pre-travel activity time)
Time taken by the occupants for activities carried out before starting the movement of exodus.


Fire safety engineering: phases of the applied methodology
The performance design methodology consists of two phases:

1) The first phase consists in the preliminary analysis whereby the steps leading to the identification of the most representative conditions of the risk to which the activity is exposed and what are the performance thresholds to be used in relation to the safety aims to be pursued;

2) The second phase consists in the quantitative analysis whereby the analysis of the effects of the fire is carried out using calculation models by comparing the obtained results with the performance thresholds already identified and by defining the project to be definitively approved.

First phase: preliminary analysis

The preliminary analysis phase consists of the following sub-phases necessary to define the risks to be tackled and, consequently, the objectives criteria for the quantification of the risks necessary for the subsequent numerical analysis.

Define project scope

This sub-phase defines the purpose of fire-fighting design in which the fire-fighting professional identifies and documents at least the following:

a) The intended use of the asset;
b) The purpose of fire-fighting performance design;
c) Any project constraint arising from regulatory requirements or from specific needs of the activity;
d) Fire hazards associated with the intended use;
e) Boundary conditions for the identification of the data necessary for the evaluation of the effects that could be produced;
f) The characteristics of the occupants in relation to the type of building and the intended use.

Identification of fire-fighting safety goals (Identify goals, defined objectives)
After establishing the purpose of the project, in particular the intended purpose of the activity, the fire-fighting safety professional shall specify the fire-fighting safety objectives, among those provided by the Code, in relation to the specific needs of the activity under consideration and the design purpose. The fire-fighting safety objectives allow to specify qualitatively, for example, the level of protection of the occupants’ safety, the maximum tolerable damage to the activity and its content, the continuity of operations following an incidental event.

Definition of performance thresholds (Develop perform criteria)
The next step is the translation of fire-fighting safety objectives into performance thresholds (performance criteria) of a quantitative and qualitative type regarding which the objective fire-fighting safety assessment can be carried out. The choice of performance thresholds quantifies thermal effects on structures, fire propagation, damage to occupants, prosperity and environment. These performance thresholds should be able to be used in the second stage of the design to objectively discriminate between design solutions that meet fire-fighting objectives and those that do not achieve the required performance. For the purpose of design for the protection of life, established life performance thresholds (life safety criteria) are used to define the incapacitation of occupants exposed to fire and its products. By definition, the occupants become incapacitated when they become unable to secure themselves independently and this condition causes, in a short time, the death of the subject.

Identification of design fire scenario (Develop fire scenarios)
Fire scenarios represent the schematisation of events that may reasonably occur in the activity in relation to the characteristics of the fireplace, the building and the occupants.

Second phase: quantitative analysis
The quantitative analysis phase consists of some sub-phases necessary to carry out the scenarios security checks identified in the preliminary phase.

Develop trial designs
Fire-fighting professional shall develop one or more design solutions for the activity, according to the aim of the project, to be subject to subsequent verification to meet fire-fighting safety objectives.

Evaluation of design solutions (Evaluate trial designs)
At this phase, the fire-fighting professional calculates the effects which the design fire scenarios determine in the activity for each design solution developed at the previous stage, using an analytical or numerical calculation model: the application of the model shall provide quantitative results for describing the evolution of the fire and its effects on structures, occupants or environment, according to the design purpose. Modelling the effects of fire allows the effects of individual scenario to be calculated for each design solution.

The modelling results are used to verify the compliance with the performance thresholds of design solutions for each design fire scenario, by selecting only those design solutions that meet all performance thresholds of each design fire scenario and discording all others.

Selection of suitable design solutions (Select final design)
The fire-fighting professional selects the final design solution from those that have been positively verified with respect to the design fire scenarios.

Fire-fighting safety engineering: design regulations and documentation

The design documentation shall be supplemented by:

a) For the first phase (preliminary analysis): technical summary, signed jointly by the fire professional and the person responsible for the activity, where the performed process to identify the design fire scenarios and performance thresholds is summarized;
b) For the second phase (quantitative analysis): specific technical report where the results of the analysis and the design process are shown; fire-fighting safety management programme, with the specific arrangements for the implementing fire-fighting safety management measures.