Passive Fire Protection | What is Passive Fire Protection

Why do we need fire protection?
The fundamental purpose of fire protection systems whether active or passive is to firstly, prevent the passage and spread of smoke and fire, from one area of the building to another, to allow for the safe escape of the building occupants. Secondly to prevent / reduce the amount of damage to the building structure, neighbouring structures and reduce the risk of collapse for the emergency services.

A number of the fundamental requirements of fire protection are specified in approved document B of the Building Regulations

  • Means of escape.

  • Internal surface spread of flame to linings.
  • Structural integrity of the building.
  • Fire compartmentation.
  • Access and facilities for emergency services.

Other more commercial reasons for the use of fire protection systems, is to reduce the amount of damage and prevent collapse of the building. This intern can help to:

  • Reduce the rising cost of insurance polices.
  • Protect capital investment.
  • Reduce the possible risk to the fire fighters.

So what is fire protection?
A buildings fire protection comes in 2 specific forms, active and passive systems:

Active systems in the form of, suppression, extinguishers, sprinkler, alarm and extract ventilation.

The overall aim of active systems is to extinguish the fire by:

  • Detecting the fire early and evacuating the building.
  • Alerting emergency services at an early stage of the fire.
  • Control the movement of smoke and fire.
  • Suppress and/or starve the fire of oxygen and fuel.

Passive systems in the form of fire rated doors, barrier, ceilings and structural fire protection.

The overall aim of passive systems is to contain the fire by:

  • Use of fire rated partitions and doors to prevent the fire and smoke from moving from one compartment to another.
  • Delaying the collapse of the building structure.
  • Delaying the growth of the fire.

Passive fire protection
Nullifire have been instrumental in the development of 2 key areas of passive fire protection over the past 30 years:

  • Intumescent coatings for the protection of structural steelwork

  • Fire stopping and penetration sealing systems.

Why do we need to protect the steelwork?
During a fire situation the temperature within a building can rise from ambient around 20oC, up to 1000 oC. As the temperature in the building increases, so does the temperature of the steel structure that supports the building. All steel sections have wants know as a critical steel temperature. This is the temperature at which the steel section begins to loose its strength and buckle.

The building regulations require that structural steel is protected against fire, to ensure that the load-bearing strength of the steel is not decreased as the temperature increases.

There are 3 main systems used to protect structural steelwork against the risk of fire:

  • Boarding:
    • In the form of plasterboard / mineral fibre / Calcium silicate etc.
  • Spray:
    • In the form of cementitious, mineral fibre or gypsum systems.
  • Intumescents:
    • Thin film intumescent basecoats.

Determination of fire protection measures
The type of protection to use normally comes down to the following factors:

  • Fire performance required, 30/60/90/120 or 240 minutes.

  • Type of steel member to be protected.
  • The design and aesthetic requirements.
  • Weight restrictions.
  • Construction time.
  • Cost considerations.
  • Steel location, Internal or External

Cementitious spray systems are generally the cheapest method of protecting steelwork at 90 up to 240 minutes fire performance. However the appearance of such systems frequently rules them out of consideration.

Advantages

  • Low cost.
  • Can be applied to complex shapes.
  • Assists thermal and acoustic insulation.
  • Up to 240 minutes.

Disadvantages

  • Only suitable for steel members out of site.
  • Very messy application.
  • Easily damaged.
  • Difficult to ensure uniform thickness.
  • Wire reinforcement may be required for larger member.
  • Space required for given protection.

Boarding fire-protection solutions are promoted as a clean dry process, that can provide a neat aesthetic finish with the required fire performance all in one. However they are impractical for the protection of castellated beams or the increasing used cellular beams where the holes are used for services penetrations.

Advantages

  • Clean, dry installation.
  • Fire performance and finish all in one.
  • Up to 240 minutes fire performance.
  • Pre-formed section available.

Disadvantages

  • Hides the feature of the steel member.
  • No good on complex shapes.
  • Long application time.
  • Thickness at higher performance can be an issue.
  • Weight can be an issue with dense boards.

The general rule of thumb is that intumescent coatings are the most efficient systems at 30, 60 and now most 90 minutes applications. Thin film intumescent coatings have reduced in price over the past few years as a result of increased competition and improved technology. These systems offer a durable, light weight solution, whilst allowing the steel member to remain a feature of the building design.

Advantages

  • Ideal where the exposed profile of the steel is a feature of the building design.
  • Only system suitable for castellated and cellular beams where the holes are used for services.
  • Light weight compared to other products.
  • Thin film system reduces the amount of space used.
  • Up to 10 times faster to apply than boarding systems.
  • Decorative top seals available.
  • Fibre free, no dust.
  • Easy to clean and maintain.

Disadvantages

  • Skilled application required for best results.
  • Quality checks required.
  • Primer compatibility checks required.
  • Drying times.
  • Site over-spray issues.
  • Masking may be required to surrounding areas.

For further details on Intumescent coatings go to ‘How Intumescent Work’.

For further information on Intumescent coating and fire stopping solutions please refer to the relevant product sections.