The LWF Blog

Fire Safety Engineering for Design – Fire Safety Design Process – Part 49

October 4, 2021 11:31 am

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 48, LWF began to address the fire safety design process and the four main stages involved. In part 49, we look at ‘Quantitative Analysis’ and ‘Assessment Against Criteria’; parts two and three of the four stage process when approaching a fire safety engineered design.

Quantitative Analysis

The first stage of a fire engineered design process is known as Qualitative Design Review (QDR). Following QDR, a quantified analysis can be undertaken where necessary. A quantitative analysis may be considered necessary to support and establish the extent of an area of the proposed design solution, although it may be that a satisfactory design solution can be established without quantification.

Assessment Against Criteria

Following QDR and quantitative analysis is a process known as ‘assessment against criteria’. This means that the fire safety design is assessed against the objectives and design criteria identified during the QDR process.

The acceptability of a design can be judged using three basic approaches: Comparative, deterministic and probabilistic.

Comparative criteria enables the designer to show a level of fire safety achieved in the design by comparing it against another building that complies with recognised fire safety design codes. This method is often used where it is difficult to describe the level of safety in absolute terms.

Deterministic criteria is used to show a set of circumstances and the outcome. For instance, the initial worst case scenario assumptions will not result in the smoke layer falling below head height during the allowed evacuation period, based on the proposed design.

Probabilistic criteria set out to show the probability of an event occurring are acceptably low. The risk criteria are expressed, commonly, in terms of the annual probability of an unwanted event occurring. An example might be that the probability of death in fire is less than a given percentage per annum.

It should be noted that the fire engineering design process can involve a repeat of the first three stages until a suitable and acceptable design is reached and the final stage – reporting of results – can begin.

In part 50 of LWF’s series on fire engineering, we will look at the reporting of results, which is the final stage of the fire safety engineering design process. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.

Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact the LWF office on 0800 410 1130.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.