To understand what a building's fire zone is, you need to analyze what requirements are placed on modern projects in terms of fire safety. At the beginning, it is worth considering how it will be used, who will use it, and what are the requirements for security systems. During the design, construction and operation process, specialized solutions are used to ensure:

  • maintaining the load-bearing capacity of the structure for a specified period of time,
  • limiting the spread of fire and smoke inside the building,
  • limiting the spread of fire to neighboring buildings or adjacent areas,
  • the ability to evacuate people or save them in another way,
  • taking into account the safety of rescuers.

It can be assumed thatfire safety includes all activities and undertakings aimed at protecting life and health, property and the environment against the effects of the occurrence and spread of fire. It is worth mentioning that in Poland one of the most important legal acts regulating issues of fire safety and building security systems are Technical conditions that should be met by buildings and their location (Journal of Laws 2022, item 1225) - hereinafter referred to as TU.

What is a fire zone?

The use of appropriate preventive measures allows, in hazardous conditions, to contain the fire and the impact of high temperature within the fire zone at least for the assumed time. This, in turn, allows you to significantly minimize the risk and possible losses to the area provided for in the project. Fire zone is a building or part of it that has been separated by separation elements or strips of free area. The exact definition can be found in the TC (§226).

Photo: Division into fire zones

Simply put, a fire zone may include [3]:

  • room,
  • storey,
  • part of the building,
  • the whole building,
  • a complex of buildings standing on the same building plot.

It is assumed that when a fire breaks out, it will cover one fire zone, which is also the maximum loss area. Dividing the building into fire zones allows you to better adapt the devices used to a specific area, better configure alarm systems, and better manage evacuation operations. By definition, evacuation from a fire zone to an adjacent zone helps ensure safety. The adjacent area (fire zone) is separated with high temperature resistant partitions, which helps contain the fire. A separate concept is a room separated for fire (e.g. fire vestibule), which does not constitute a separate fire zone.

Division into fire zones

Fire separation elements such as walls and ceilings or an appropriate distance between buildings allow for division into fire zones. The building may be divided into several fire zones, each of which is an area with a specific area. It is calculated as the internal area of ​​the building or its part, and also includes the mezzanine area.

Due to their purpose and use, buildings and their parts constituting separate fire zones are divided into [1]:

  • residential, collective housing and public utilities characterized by the human hazard category, referred to as ZL,
  • production and storage, referred to as PM,
  • livestock (used for breeding livestock), hereinafter referred to as IN.

Additionally, buildings and their parts constituting separate fire zones, referred to as ZL, are classified in one or more than one human hazard category:

  • ZL I – containing rooms intended for the simultaneous stay of more than 50 people who are not their regular users, and not intended primarily for use by people with limited mobility;
  • ZL III – public utility, not classified as ZL I and ZL II;
  • ZL IV – residential;
  • ZL V – collective residence, not classified as ZL I and ZL II.

Permissible area of ​​fire zones

In certain cases, the area of ​​the ZL fire zone may be up to 10,000 m2. This value may be increased provided that permanent, automatic water extinguishing devices are used (by 100%) or automatic smoke removal devices activated by smoke detection systems (by 100%). When using the above-mentioned simultaneously solutions, it is allowed to increase the area of ​​fire zones by 200%. It is worth mentioning that in the case of PM fire zones (except for garages), the permissible area of ​​the fire zone depends on the fire load density Q [MJ/m2]. Permissible areas for ZL, PM, IN zones are specified in the WT (§227-231).

Passive and active fire protection

In order to ensure the highest possible level of fire safety, fire protection systems are used in a given building, which may consist of passive and active security measures. The purpose of using passive protection is to increase the fire resistance of structure elements and slow down the spread of fire and high temperature. Properly thought-out and implemented fire protection systems allow you to reduce the threat to the size of the fire zone. Passive protection measures include: partition walls, spray masses, dust coverings, and intumescent and absorbent coatings.

Active protection measures include all fire protection systems and their components, i.e. fire alarm systems, SUG fixed fire extinguishing devices, sprinkler devices, internal hydrants, and smoke removal systems. The above-mentioned fire protection systems require activation during a fire (through devices detecting fire or human activity, e.g. pressing a manual fire alarm call point.

Fire resistance class

Fire resistance can be described as the ability of an element to maintain a specific functional property under fire conditions for a specified period of time, expressed in minutes, determined on the basis of testing a test element.

Dividing the building into fire zones or designating escape routes would not be possible without the use of separating elements that are able to maintain the required fire resistance for the necessary time in fire conditions. Thanks to them, it is possible to stop a fire within a given zone. Building elements should be made of non-flammable materials and have a fire resistance class appropriate to the fire resistance class of the building.

The class notation consists of [2]:

  • R – fire load capacity, i.e. the ability of a test load-bearing structure element to maintain the test load without exceeding specified criteria due to the size and speed of movement (in minutes),
  • E - fire tightness, i.e. the ability of a test element separating an element of a building structure to prevent the passage of flames and hot gases and to prevent the appearance of flames on an unheated surface (in minutes),
  • I - fire insulation, i.e. the ability of a test element separating a building structure element exposed to fire on one side to limit the temperature increase of the unheated surface below specified levels (in minutes).

Elements of fire separation and closing the openings in them must have a fire resistance class (REI30-REI240). Fire doors or other fire protection closures must have a fire resistance class (EI30-EI120) and the fire separation wall (REI60-REI240). The required fire resistance classes are specified in the WT (§232). It is worth mentioning that the fire separation wall should be built on its own foundation or on a ceiling based on a load-bearing structure with a fire resistance class not lower than the fire resistance of this wall.

Summary

In order to design a facility that will meet legal requirements in the field of fire safety, it is necessary to take into account aspects that ultimately affect the behavior of the structure, the spread of smoke and fire, the possibility of evacuation, and the safety of rescue teams in fire conditions. One of the most important issues is appropriate fire protection, including the division of the building into fire zones. Properly determining the areas to be separated from fire allows you to select appropriate technical solutions (including alarm systems), and also significantly facilitates the supervision of the operation of individual devices. Additionally, a well-thought-out division directly affects the safety of building users who, if necessary, will be provided with appropriate evacuation conditions between adjacent zones. By using the right solutions, there is a good chance of stopping the fire, especially its spread between zones. It should be remembered that all partitions, such as a separating wall, must have an appropriate fire resistance class, and the fire zone cannot exceed the permissible area specified in the Technical Conditions.

Check also: How does the fire alarm system work?