fire glossary


Glossary of Fire Safety Terms

These definitions are provided to assist in understanding some of the technical terms used in fire safety. They are not exhaustive and more specfic definitions may be available elsewhere.

A room which serves as part of the escape route from an inner room.

A storey with a floor which at some point is more than 1,200mm below the highest level of ground adjacent to the outside walls, unless, and for escape purposes only, such area has adequate, independent and separate means of escape.

Any window provided for emergency escape purposes should have an unobstructed openable area that is at least 0.33m2 and be at least 0.45m high and wide. The bottom of the openable area should not be more than 1.1m above the floor.

An exit from a building where people are no longer in danger from fire or smoke.

A building, or part of a building, constructed to prevent the spread of fire to or from another part of the same building or an adjoining building.

A door, frame and furniture which, when closed, is intended to restrict the passage of fire and smoke to a known level of performance.

Automatic fire suppression systems control or extinguish fires without human intervention. Examples include Automist®, sprinkler systems, mist sprinkler systems, and gas based systems.

A building or part of a building which is occupied by more than one household and where at least one of the households share or lacks access to basic amenities (cooking, toilet etc.) and occupation by the households is as their main residence and it is the sole residential use of the accommodation.

An HMO occupied by unconnected individuals, each living essentially separate lives but where the individual lettings are not self contained. Commonly, each bedsit will have cooking/food preparation facilities, washing facilities and living/sleeping space, but bathrooms and WCs will be shared between several bedsits.

Occupiers of the same family including spouses, co-habitees, same-sex couples and any blood relative.

A room from which escape is possible only by passing through another room (the access room).

Route(s) provided to ensure safe egress from the premises or other locations to a place of total safety.


A popular arrangement whereby more than one room function is arranged within the same fire compartment. This could commonly be a kitchen/diner arrangement, or a staircase that passes through a habitable room. Open plan layouts have aesthetic benefits but pose fire safety challenges. For more information on open plan, please visit the Open Plan Alliance.

Personal protection systems (PPS) are local application watermist systems designed to protect a specific area within an enclosed volumetric space (i.e. a room) from fire. These portal fire suppression systems, such as Automist® PPS, are also sometimes called mobile watermist systems (MWS).

A typical application would be to protect a vulnerable person who spends the majority of their time in either a bed or chair and because of mental and/or physical health issues are more prone to starting fires accidently and/or unable to escape in the event of one. The fire hazard can therefore be considered to be localised to a specific area within the home.

This terminology is used to describe Automist.

A fire-resisting enclosure providing access to an escape stairway or corridor, with two sets of fire doors between the corridor and any habitable rooms.

A stairway which is adequately protected from the rest of the building by fire-resisting construction.

An escape route which is adequately protected from the rest of the building by fire-resisting construction.

This term is used to describe the limit of the measures that must be taken to reduce risk. For example, under the RRFSO, risks must be reduced until the cost and effort to further reduce the risk would become grossly disproportionate to the benefit achieved. At this point it is said that further improvements are not reasonably practicable.

The person ultimately responsible for fire safety as defined in the Regulatory Reform (Fire Safety) Order 2005.

A separate floor of a premises. Although most regulations are written in terms of floor heights, it is helpful to be able to translate this into more conventional terminology. A house in which no floor level is above 4.5m will generally be a two-storey property, which may also have a basement (the ground floor is the storey where the final exit is located). A property with exactly one storey above 4.5m is commonly equated to a three-storey premises. Therefore, a house with a basement, ground and two upper floors with its entrance/final exit at ground floor level should be regarded as a three-storey house.

Smart fire sprinkler systems pinpoint the location of the fire in a building and douse the blaze with fire suppressant. This targeting reduces the wastage of this suppressant and minimises damage. In 2016, global technology research and advisory company Technavio identified smart systems in the residential setting as emerging trends that had the potential to significantly impact the fire suppression market. It singled out Automist Smartscan as the vanguard of this wave. The device is also future-proofed to be linked up with a domestic smart home (IoT) devices such as the Nest thermostat. It can even send alerts to the homeowner's smartphone to alert them if a fire occurs or if the system needs critical maintenance.

A fire suppression technology using pressurised water to create small water droplets. This offers multiple benefits over conventional sprinklers, including higher droplet surface area per unit volume, and the ability to have the mist drawn with air into the flame through convection.

The NFPA defines water mist as a water spray in which virtually all the water exists as droplets of less than 1000 micron diameter. Three pressure regimes are commonly referred to:

  • Low pressure: 12 bar or below
  • Medium pressure: above 12 and below 34.5 bar
  • High pressure: 34.5 bar and above

Automist is a high pressure system, operating at around 90 bar.