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The Use of Intumescent Ventilation Grills / Grilles for Air Transfer Systems

A building’s air transfer system e.g. in an office block building needs to allow the circulation of air thus keeping the air quality levels up, but also needs to control the temperature e.g. to keep a comfortable working temperature and not to increase energy costs by losing heat. The air transfers system may use fan assisted ventilation ducts, or a natural effect e.g. ‘stack effect’ (a temperature induced method of making the different internal pressure differentials work so that the warm air can rise up through the building – using ventilation grills as part of the system). Some important points to make about the air transfer system and it use of grills / grilles are:

  • The grills may be used e.g. in timber doors, stud walls, some duct terminals within (not on the boundary of) fire protected route. The apertures / spaces made in walls in doors for ventilation purposes therefore also provide a possible route for fire and smoke and therefore steps need to be taken to contain the fire and smoke effectively e.g. using Intumescent Grills.
  • A ventilation grill generally consists of the grill itself and the faceplate(s).
  • Hot air expands and the higher pressure means that the hot (high pressure) air will naturally try to flow towards cooler (low pressure) air. The implications of this are that air transfer systems have to be able to maintain the right pressure differential balance, and all gaps created in the fitting of grills which could be exploited by fire and smoke need to be adequately addressed.
  • Even though intumescent materials can be used effectively in the systems their expansion is activated by heat. ‘Cold smoke’ aspects therefore could be combated by using e.g. smoke seals or electro-mechanical systems linked to smoke detectors alongside the intumescent ‘failsafe’ part of the system.

Intumescent Ventilation Grills

The benefit of ventilation grills made from intumescent material is that this material’s natural and normal reaction to temperatures (associated with fires) is to expand in volume well beyond their normal size to create a large amount of char which restricts flames, gases and smoke.

The openings in Fireplug Intumescent Ventilation Grills for example will provide a good level of free airflow in normal use (50% for 100 x 100mm and 76% + for 300 x 300 mm) but will seal up under the action of heat during a fire. These are used in conjunction with Fireplug FP Pressed Steel Louvered Faceplates. Fireplug FPG suit most fire doors and the Fireplug FP (faceplates) can be easily surface mounted on either side. It’s important to cut a hole which provides a snug fit and in composite doors it’s recommended that the internal faces of the aperture are framed with a dense hardwood. Intumescent Mastic can be placed between the grill and the wood if needed.

Complete Fire Protection Ltd. Unit 2, Ferry Steps Industrial Eastate, Albert Road St Philips, Bristol BS2 0XW
Tel 0117 971 1917 Fax 0117 971 1727 or for more products, information and support email us.