What is an intumescent?

An intumescent is a substance that expands in the presence of heat to produce a layer of char. They have become widely used in passive fire protection products with the char acting as insulation from the heat of the fire.  There are two main types of intumescent:

• Soft char producers; the light char produced is a good insulator. They usually contain a high proportion of hydrates which release water vapour when heated. This results in a cooling effect which adds to the insulating property of the char.
• Hard char producers are made with sodium silicates and graphite. In contrast to the soft char producers they are able to exert an expansion pressure which can be utilised in fire stopping applications. Plastic pipes are crushed in the event of a fire to stop it spreading through a floor or wall.

 Demonstration of intumescent fireproofing

Here a small amount of the intumescent material used in the Hilti CP643 fire collar (a hard char producer) is placed in a heated glass causing it to rapidly expand:

Below is a time lapse recording of the Hilti CP643 fire collar in action. After six minutes the plastic pipe has burned away but the intumescent material has filled the hole in the wall, preventing or delaying the spread of smoke and flames. This remains for one to two hours after the fire has started.

Intumescent products

Intumescent coatings:

• paints for steel (protect the structural steel of buildings, preventing or delaying it’s collapse)
• paints for timber
• paints for walls and ceilings
• varnishes

Intumescent products for doors (maintaining fire door integrity):

• fire seals and smoke seals
• pads (for fire door hinges)
• glazing tape and glazing channels
• letter boxes and letterbox liners

Intumescent products for doors (upgrading to or making fire doors):

• paint and varnish
• paper

Intumescent fire stop products:

• pipe collars and pipe wrap
• duct sleeves and duct wrap
• pillows, pads and fire stop block.
• fire grilles

Intumescent electrical protection products:

• socket box covers
• cable basket sleeves
• cable tray sleeves.

Intumescent lighting protection products:

• downlight covers
• fire hoods

Other intumescent products:

• mastic
• putty
• sealants
• foams

Videos:
Hilti
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