Restriction of a fire and minimization of fire and smoke spread is a key target in all building codes and regulations. The easiest way to solve this challenge and the most cost-efficient solution for architects and designers is fire compartmentation. It is mandated in all national building regulations all over the world and provides precautions, limitations, clear rules on the size and location and type of construction of fire compartments. It is as well a concern for building owners and insurance companies, not only in respect to life safety, but also in respect to asset protection. But why is it so important, what are the benefits and the hidden risks of fire compartments?

THE THEORY OF FIRE COMPARTMENTATION IN CODES AND REGULATIONS

Every building must be constructed in such way, that in the event of a fire in the building, fire and smoke is limited from spreading. The spread of fire and smoke can be restricted by dividing a building into separate compartments with fire-resistive walls and floors—increasing the availability of escape routes for occupants. In that respect, compartmentation protects escape routes such as corridors or stairs.
Technically speaking, compartments stop the fire spreading, limit the fuel supply and cut off the supply of oxygen therefore attack the three main sources of a fire: heat, fuel and oxygen.
Therefore, the concept of fire compartments has found its way into all building codes and regulations as one of the most important principles of passive fire protection. Already one of the first general fire regulations in Bavaria, Germany from 1791 said, that certain areas in a building must be separated so that fire cannot spread over from one area to the other.

In summary: a fire compartment is an area within a building which is completely surrounded with fire-resistant construction. Fire compartments are required by law in some types of buildings, and strongly recommended in others as a basic safety measure. Some insurance companies may also demand that fire compartments be installed before they will write policies for certain types of businesses, in the interests of reducing their liability.1)

THE PRINCIPLE OF FIRE WALLS AND FLOORS IN A BUILDING

The goals are not absolute but related to time. They are to guarantee:

• building will not collapse or become unstable.
• protect fire fighters and escape routes, reduces the chance of fires growing and creating a danger to occupants and people in the vicinity of the building: more than 40% of deaths were people who were not in the room of origin
• safe property: many billion $ insured losses but also many times more uninsured losses per year
• stop the spread of smoke: smoke travels between 50 and 300ft per minute, 2/3 of fire related deaths are through smoke inhalation

In many regulations, a building should be divided by compartment walls and floors. These walls and floors must have a minimum fire resistance duration. But buildings are different in type, purpose, size and life risk to occupants. In most cases, for example, a single-storey family house poses less life risk than a multi-storey large-scale hospital or shopping centre.

WHAT ARE THE HIDDEN HAZARDS OF FIRE COMPARTMENTS?

Compartment walls and floors are intended to prevent the passage of fire and smoke from one compartment to another. But these compartment walls and floors also leave openings for required cable, duct or pipe works, so called service penetrations. These required service penetrations should be kept to a minimum but are just required and necessary in a building. Lighting, electrical supply, heating and water distribution, ventilation and air conditioning, telecommunication lines and many other services are also installed in buildings and have to pass from compartment to compartment in defined or sometimes not-at-all defined ad-hoc created openings.

On top, many trades and contractors are involved in the installation of the different services, like drywallers, insulators, electricians and HVAC contractors. This makes the actual firestopping a quite complex job which can only be solved with clear pre-planning or specification. Many times, the correct and compliant closing of the service penetrations according to the required fire rating is left to the last party on the jobsite.

As firestopping materials do have approvals and are tested according to clearly defined test standards, the correct installation is sometimes not an easy task. Therefore, the brutal fact is that many firestop penetrations through fire rated compartments remain incorrectly firestopped, firestopped with wrong material and not according to the relevant approval or even remain open. This then represents one of the major risks in a building as fire and smoke is free to travel all over the building and the compartment will not fulfill its intended and legally required purpose anymore.

Typical high-risk areas in compartments: unsealed pipe, cable penetrations and joints in between building elements

Typical high-risk areas in compartments: unsealed pipe, cable penetrations and joints in between building elements

The correct installation of firestop is important. In case of a fire, plastic pipes or cables melt and create toxic gases. Metal pipes and high voltage cables transfer heat. Firestop materials expand and automatically close off the openings and assure the correct fire integrity of the wall or floor. Firestop also provides resistance to the transfer of excessive heat and the ability to provide insulation from high temperatures.

Smoke tightness should never be forgotten as smoke (cold smoke) is one of the key killers in an event of fire (toxicity). Smoke travels fast and even long before the fire becomes a danger. On top smoke will also destroy assets and equipment throughout the building compartments. Therefore, a tight seal must be ensured.

In the picture below, a real case fire with the impact of cold smoke, far away from the origin of the actual fire was documented: within not even 2 minutes the hallways and all areas in this hospital were basically full of toxic smoke. Reason; unsealed service penetrations.

Read part 2

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Sources:
 
1) wiseGEEK, 2003 - 2016 Conjecture Corporation
2) Safety Investigation Authority, Finland, www.turvallisuustutkinta.fi
3) Feuer Trutz Brandschutzatlas 3/2012
 

Other sources and pictures: internal Hilti Aktiengesellschaft, Schaan, Liechtenstein