Fire compartments in plants and warehouses — what they are, how they are formed, how they differ from ATEX zones and how to supervise them

Short answer: they are different concepts under different rules and are often confused. A fire compartment is a part of the building defined by fire-resisting walls and floors; it covers whole rooms and storeys. A hazardous area (ATEX zone 0, 1, 2 or 20, 21, 22) is where an explosive atmosphere of gas, vapour or dust may occur — often only a few metres around a tank, valve or charging hatch.

Fire compartments follow building technical conditions and appear in the building design. Hazardous areas are classified by the employer or operator in the explosion risk assessment and explosion protection document. One compartment may contain several ATEX zones, and a room at risk of explosion usually needs fire separation as well.

Supervision differs too. In a fire compartment you keep walls, doors and penetrations intact; in an ATEX zone you select and inspect explosion-protected equipment — covered in the guide to ATEX equipment inspections and the Ex register.

Short answer: Polish technical conditions divide buildings and parts forming separate compartments into three groups. ZL covers residential, collective accommodation and public buildings intended mainly for people. PM covers production and storage buildings. IN covers livestock buildings.

ZL is further split by use: ZL I — rooms for more than 50 people who are not regular users at the same time (conference halls, shopping centres); ZL II — people with limited mobility (hospitals, nurseries, care homes); ZL III — other public buildings, including offices; ZL IV — residential buildings; ZL V — collective accommodation such as hotels and workers' hostels.

A single plant often contains several categories. The production hall is PM, while a separate office and welfare building, a canteen for hundreds of people or a training room may be ZL III or ZL I with different evacuation and fire resistance requirements. A supervisor's office inside the hall usually stays part of the PM compartment, but the designer decides under the rules.

Short answer: for PM buildings the permitted compartment area is set in a table in § 228 of the technical conditions. It depends mainly on fire load density — the more combustible material per square metre, the smaller the compartment — and on the number of storeys and building height. Separate rules apply to compartments containing rooms at risk of explosion.

Fire load density is the heat that could be released by burning all combustible materials in the compartment divided by its area, expressed in MJ/m². It is calculated under PN-B-02852 from the type and quantity of stored materials — so switching a warehouse from metal parts to plastics or cardboard packaging can exceed the design assumptions without any construction work.

The rules allow the permitted PM area to be increased when the compartment has an automatic sprinkler system (by 100%) or automatic smoke extraction (by 50%). Exact limits, how increases combine and exceptions must always be checked in the current text of § 228 and the building design — this guide explains the principle and does not replace a designer or fire safety expert.

Short answer: the letters describe fire resistance criteria and the number gives minutes. R is load-bearing capacity; E is integrity, meaning no passage of flames and hot gases; I is insulation, limiting temperature rise on the unexposed side. An REI 120 wall keeps all three for 120 minutes; an EI 60 door keeps integrity and insulation for 60 minutes.

Fire separation consists of fire walls and floors of the required class, fire doors, shutters and hatches in openings, spandrel and blank facade strips where compartments meet external walls, and service penetrations — cable and pipe passages sealed to the rating of the element. The technical conditions specify when penetrations need the rating and which class doors in a given wall must have.

The weak point is usually not the wall but what passes through it. A new cable pulled through an unsealed hole, a shutter knocked out of alignment by a forklift or a fire door wedged open means the compartment no longer works, even though it still exists on the drawing.

Short answer: the Polish regulation on fire protection of buildings prohibits, among other things, obstructing access to doors, exits and fire protection equipment and blocking fire doors so they cannot close automatically. Doors that must stay open during work are fitted with electromagnetic hold-open devices released by the fire alarm system, not wedges or string.

Fire doors and shutters with control systems are fire protection devices that receive technical inspection and maintenance per the manufacturer's instructions at least once a year. The site fire safety instruction should describe the conditions arising from compartmentation, and explosion risk and fire load should be updated after changes to processes or storage.

In practice the biggest risk comes with change: new high-bay racking, a relocated packaging store, a wall opened for services or contractor work. Changes affecting compartments should pass through management of change, and penetrations should be checked after installation work as part of contractor supervision. Extinguisher, hydrant and other equipment inspections are covered in the guide to fire equipment inspections.

In the Plans and zones module compartment boundaries are drawn on the site plan with their category (PM or ZL), together with fire doors and shutters, smoke vents, penetrations and firefighting equipment. One plan shows what belongs to which compartment and who is responsible for each section of fire wall.

Fire doors, shutters and other fire protection devices go into the inspection register with annual maintenance dates and reminders. A QR code at each door opens a short checklist during rounds: self-closing, no wedges, seal condition, clear passage. Any employee can use hazard reporting to send a photo of a blocked door or damaged penetration without logging in.

The software organises the plan, deadlines and reports but does not define compartments or calculate fire load. Compartmentation comes from the building design, and changes require a designer and a fire safety expert.