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Fire Safety in Blocks of Flats – Means of Escape – Smoke Control – Part 8

Posted: 01/10/2014 15:13

This week’s blog about fire safety in blocks of flats looks at smoke control within escape routes. Current design guidance and previous standards both state that measures should be taken to ensure escape routes can be kept free from smoke. 

With design progression thoughts about how this should be achieved have changed and we will concentrate today on the current guidance. However, this does not mean that a system which was installed previously is now obsolete. If the process was acceptable at the time of installation, and the results are effective, it remains a fire safe solution to the smoke control issue.

Current legislation is based on smoke ventilation, i.e. an acceptance that some smoke may enter the common corridor/lobby, and providing the means to ventilate by natural or mechanical means, thereby protecting the stair.

Natural ventilation, as the term implies, is removal of smoke in an area through vents or windows directly to open air, or to shafts which rise through the building to open air. The vents or openings would usually be a minimum of 1.5m2. There is potential to reduce the size of the vents, however, this is subject to specific fire engineering design. Two types of vents are typically used, dependant on the individual circumstances:

Manually Open Vents (OV’s) which, as the name suggests, are opened manually. These are most commonly found in blocks where there is more than one staircase, where the criticality of the stair is reduced.

Automatic Opening Vents (AOV’s) are those vents which are automatically opened by a system when smoke is detected. These are most commonly found in corridors and lobbies where reliance is placed on a single stairway exit from a block of flats.

Although the stairways themselves are protected to prevent smoke from entering on a normal basis, when evacuation is in progress or the Fire Service are in attendance to fight a fire, it is feasible that smoke could enter the stairway. To mitigate this concern, each stairway should have a vent of at least 1m2 at the head of the stair. As with the venting options given above, current guidance states that automatic venting is necessary in blocks with one stairway, whereas manual venting is acceptable in those blocks with multiple stairways.

Mechanical ventilation systems are used in circumstances where natural ventilation is not possible, or where the design lends itself to a mechanical solution, there are advantages also, such as they are less influenced by external factors such as the effects of wind, as well as potentially saving space due to the increased efficiency of the solution.

Next week’s blog will look at surface finishes in escape corridors, stairways and lobbies and how this can impact upon the fire safety of a block of flats. In the meantime, if you have any queries about this blog or would like to know more about the Complete Fire Safety Management online fire risk assessment platform, please contact Peter Gyere in the first instance on 0208 668 8663.

The Complete Fire Safety Management Platform is the only fully comprehensive online fire risk assessment and fire risk management platform. Our aim, at CFSM, is to make the process of becoming fire safe, straightforward and, to use our expertise in fire risk assessment and fire safety management to guide you through each step, resulting in your premises meeting all legal, insurance and ethical fire safety considerations.

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