The LWF Blog

Fire Safety Engineering for Design – Fire Engineering Design Approaches – Part 113

January 3, 2023 11:58 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 112, LWF discussed pre-movement time, which is the time between the fire alarm sounding and people beginning to move to evacuate a building. In part 113, we look at the types of occupancy and how it may affect the time required to evacuate a building.

The type of occupancy that will occupy a building may affect the approach to fire safety design. The occupants’ mobility and whether they will be familiar with their surroundings or are likely to be visitors and the simple ease of wayfinding within the premises can all influence the time needed to evacuate the building in a fire situation.

Differing occupancies exhibit certain characteristics, as follows:

• The occupancy is familiar with the building and layout and is awake, (workplaces, schools, factories etc.)
• The occupancy may be unfamiliar with their surroundings, but is awake, (shops, exhibition halls, museums, public buildings, leisure centres etc.)
• The occupancy may be sleeping and is unfamiliar with their surroundings, (hotels, B&Bs etc.)
• The occupancy is vulnerable and significant in number – will require assistance, (hospitals, care homes etc.)
• The occupancy is held in custody, (e.g. Prisons)

As well as looking at the likely occupancy of a building, the right of disabled people to access a new building in most instances, and any existing buildings as far as is reasonably practicable, means that design for escape should take into account safe egress from the building for disabled persons. It should be assumed that the potential occupancy of a new building will include a number of people with disabilities and make provision accordingly.

Complications may arise when designing safe escape for multiple-use buildings. A building that contains more than one type of occupancy (or business) may have differing and occasionally, opposing requirements. A means of escape cannot be planned to ‘fit all’ if one of the uses is closed when another is open and the route includes both premises. In such cases, independent means of escape must be provided for each.

Additionally, where security measures may compromise access to exits, compensatory exits should be provided to all occupants for use in an emergency situation such as a fire.

In part 114 of LWF’s series on fire engineering we will begin to evaluate the pre-movement time in a fire situation. 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 since 1986 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.