Designing safer buildings requires the fire-safety engineer to gain a full understanding of the user's needs and intentions in running the building, as Andy Passingham explains.


Today's buildings are complex creations. fire engineers, as a result,

need to work as part of a fully integrated team to ensure that any fire

strategy meets the functional and aspirational needs of the building,

as well as providing a safe environment for its occupants.

In many buildings, fire-incident management is an integral part of the

fire strategy. It is therefore essential that the building operator has

a full understanding of the fire strategy, and that the fire engineer

fully comprehends how their client intends to manage the building.

The fire strategy for the building touches on many elements, including

the spatial planning of the structure when examining the means of

escape, and the need to divide the building into separate fire

compartments. The structure and fabric of the building must withstand

fire to a reasonable degree, to assist egress and the actions of

fire-fighters. The systems introduced into the buildings must also be

appropriate to the level of hazard in the building.

The fire engineer's job is essentially to use fire-safety measures as a

‘kit of parts' to develop a tailored package that addresses the

specific levels of hazard in a building. Ideally, this process should

be based on prescriptive guidance, and Approved Document B and BS9999

provide accepted methods for meeting the requirements of the Building

Regulations for the various aspects of fire safety in buildings.

However, it is important to understand that these documents cannot

address all buildings, and are often based on lessons learnt from

historical fires that may not be relevant to the particular design. The

often-quoted example is the two-and-a half minute evacuation time, on

which the means of escape provision in Approved Document B is based.

The origin of this goes back to 1911, when the orchestra at the Empire

Palace Theatre in Glasgow played the National Anthem to help keep the

occupants calm during an evacuation from a fire. The process took

two-and-a-half minutes and still forms the basis of egress design

today.

The Approved Document B guidance usually states a conservative

benchmark of life safety in relation to the overall design, so, by

following the code, you can be reasonably confident that the design is

considered safe. Nevertheless, there is clear scope for a more

scientific examination of the behaviour of other elements, such as

fire, smoke, building occupants, etc, to produce a more effective and

efficient fire-safety solution.

However, whether the final fire-safety solution is based on the code

guidance or not, it is essential that it is not developed in isolation.

The fire engineer must work closely with the other building design

disciplines and the client to ensure that the fire strategy is as

simple, robust and practical as possible.

Impact of a fire strategy on building management

During the design and construction phase of a project, the emphasis is

typically on the fabric of the building. But the fire engineer must

understand how the client intends to operate their building, especially

in reaction to a fire emergency and the potential need to evacuate the

building.

It is the responsibility of the building operator – defined as the

Responsible Person under the Regulatory Reform (Fire Safety) Order 2005

– to ensure the safe evacuation of the building occupants.

Consequently, the fire strategy must reflect the management

capabilities of the client and their intended levels of staffing and

training. This is particularly important for public buildings, where

the building occupants are more likely to be unfamiliar with the

building layout, and a higher degree of management will be required.

Larger buildings may also use a phased evacuation approach, whereby

only the fire-affected part of the building will be evacuated

initially, and other areas placed on alert to evacuate if necessary.

These types of buildings always require a high level of management,

none more so than in the case of a large hospital, where evacuating

bed-ridden patients incurs its own risk to the life safety of the

patient. In this example, a highly managed form of evacuation known as

progressive horizontal evacuation is often adopted, involving the

moving of patients horizontally through a series of compartments, away

from a fire location.

To varying degrees, these processes of staff-guided evacuation

procedures are applicable to all types of buildings, particularly in

relation to the issue of evacuation of disabled occupants. A well

thought-out fire strategy will encompass these issues into the building

design, without the need for additional fire-safety measures, or overly

complex management procedures.  

Egress in action

The Curve theatre in Leicester is the first performing arts centre to

be designed in the UK by New York-based architect, Rafael Vinoly, and,

from the outset, it was clear that this would be a challenging project.

Conventional theatre design involves the full enclosure of the stage

and auditorium, with the means of escape from the auditorium either

direct to protected exit routes, or through the entrance foyer. This

traditional approach greatly simplifies the egress design, as the two

principal egress routes – at the front and rear of the auditorium – are

typically separated by fire-rated construction materials, providing

alternative escape routes.

However, the design aim of the Curve was to give the theatre a feel of

transparency by allowing the stage to be open to the foyer, while the

two halls and stage form islands, surrounded by the foyer. Rehearsal

rooms and seminar spaces are located above the halls, with the egress

stairs from these spaces and the halls leading directly into the foyer.

To allow the escape route through the foyer, a fully fire-engineered

approach was adopted, based on scenario-based populations and carefully

defined fire scenarios. The fire engineer worked closely with the

client to fully understand how the theatre operated, and analysis was

carried out to demonstrate that effective egress would occur under

real-life conditions.

Since the fire strategy for the project was completed, the theatre

staff have been trained to carry out fire risk assessments and,

following a series of workshops between the client and the fire

engineer, a management strategy for the building was created.

As the egress strategy is based on analysis rather than a code or

guidance, an additional graphic report was produced to give the client

an understanding of the population capacity of each of the key spaces

in the building, and how these relate to the overall building capacity.

This document will be used to plan special events in the building and

ensure that the various event spaces are used to their full potential.

The Curve has associations with disabled performance groups, so it

expects to have a significant number of disabled occupants in the

building. The typical approach to refuge design is to provide a single

wheelchair-sized space in each protected escape stair enclosure.

However, in a large public building this may be insufficient, so the

designers must be aware of the likely number of disabled users in a

building.

The engineering solution for the Curve used the building's natural

geometry to assist in the provision of refuges. Consequently, the

auditoria can act as refuges in the event of a fire in the foyer, and

vice versa, providing a more flexible approach to the issue of disabled

egress than the typical approach of a single refuge within each

protected stair, which would not have been sufficient for this building.

In the case of the new Mary Rose Museum in Portsmouth, scenario-based

egress was used to enable museum galleries to act as refuges. One of

the advantages of this approach is that the galleries will be staffed

by attendants trained in evacuation methods. This allows the refuges to

be situated in relatively open spaces, where visibility is good, rather

than tucked away in a stair lobby. This design approach is also

considered to be more inclusive, as the refuge is the space used by all

the building occupants, rather than a separately defined area.

From a design perspective, this method has also allowed the stairs from

the galleries to be open, as the protection for the escape routes is

provided by the gallery itself, rather than the conventional enclosure

around the stair.

Summary

The projects and approaches discussed above demonstrate how fire

engineers need to look beyond their traditional role of gaining

approval under the Building Regulations for each project. They need to

fully understand the client's needs and their anticipated operational

procedures. By considering these issues at an early stage of the

project, they can be incorporated into the design, resulting in safer

buildings that are more easily managed.

Andrew Passingham is an associate

director at Arup Fire and will be speaking on this subject at the IOSH Conference at 12pm on 25 March.