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Can Automist enable compliant open-plan flat layouts?

Open plan flats can be considered to be flats that do not contain a protected entrance hall, and escape from the flat is via an accommodation room such as a living room. When a one-storey flat combines a kitchen, dining room, and living room with beds that open directly onto it, this is called an "inner room scenario" because anyone trying to get out of the property from a bedroom must go through a high-risk area. Automist can be put in the open-plan area (sometimes with the help of a fire engineer) or in the entirety of the residence.

Open plan flat with no lobby

Open plan flat with no lobby

BS 9991:2015 states on page 47:

Open plan flats…should be fitted throughout with a Grade D LD1 fire alarm and fire detection system in accordance with BS 5839-6:2013, and an AWFSS (see 11.2, Table 2). Open-plan flats should meet the following specific recommendations.

a) The size of the open-plan flat should not exceed 16 m × 12 m.

b) Open-plan flats should be situated on a single level only.

c) The ceilings within the open-plan flat should have a minimum height of 2.25 m.

d) The kitchen should be enclosed in open-plan flats having an area exceeding 8 m × 4 m. Cooking appliances in open-plan flats having an area smaller than 8 m × 4 m should not be adjacent to the entrance of the flat.

NF19 concluded (see page 29):

Sprinkler protection may be considered as an alternative to the physical (passive) enclosure of escape routes. The presumption is that sprinklers will be able to ensure that tenable conditions are maintained in the escape routes. Sprinklers are often proposed in conjunction with fire detection on the grounds that, in a slower developing fire, the early warning system alone should provide the occupants with sufficient time to escape, and where the fire develops more quickly the sprinkler system should control the fire and maintain tenability.

For flat design, the recommendations of ADB pose a significant limitation on the conditions for adopting bedrooms as inner rooms. Because of this, the National House Building Council (NHBC) asked the Building Research Establishment (BRE) to do a study (NF19) on the risk of fires in open-plan flats. NF19 included computer modelling of several flat arrangements and fire and evacuation scenarios. Comparative analyses were used to figure out how safe traditional (i.e., ADB-protected entrance hall) and open-plan layouts were compared to each other. These studies looked at the fractional effective dose (FED) for people leaving a house where a fire started. The FED is a measure of the airborne pollutants (irritants and asphyxiants) that people breathe in. Toxins like carbon monoxide (CO) build up over time as people leave a building where a fire started.

Based on NF19, it was decided that open-plan flats could reach the same or a higher level of safety than what the advice suggested. This was made possible by the addition of active fire suppression, like Automist, and an improved automatic detection and alarm system. NF19 highlights the practice of applying performance-based analysis to support deviations from residential fire safety guidance, especially for open-plan arrangements.

Case study - Open plan Brook Green apartment
Read next - Are there any fire engineers familiar with Automist?

Disclaimer: This information is not intended to be a comprehensive guide to all aspects of the building regulations but rather a useful source of background information. Whilst every care has been taken to ensure that the contents of this FAQ are correct at the time of publication, it should never be used as any form of substitution for the guidance documents. It should be noted that there may be specific additional requirements dependent upon local authority building regulations and/or fire authority.