Smoke and fire curtains webinar Q&A

Posted by Paul Compton on 03/11/15 12:00

I received some excellent questions during the Q&A section during the recent webinar that I presented. Here you can see my answers to these questions, slightly edited for clarity.

There is also a recording of the webinar available.

Where is mandatory testing of curtains covered and what is the required frequency?

The testing of curtains is covered in BS 8524-2 and I guess this question was probably asked before I showed the table, right at the end of the presentation, which gives the recommendations for testing to BS 8524.  It is important to remember that BS 8524 is a Code of Practice and that as such it is not referred to in the Building Regulations, or “mandatory”, but in general terms any fire curtain should be tested and maintained in accordance with the table in BS 8524 Pt 2.

When considering smoke screens, should we consider thermal shock, assuming a building is sprinkler protected? 

The answer to that is no: there is nothing within the test regime which considers thermal shock from a sprinkler.  If there is a sprinkler system, then the smoke temperatures are never going to get up to the very high temperature that the curtain is tested to - 600oC. 

If a sprinkler system is installed, then we would not expect the smoke temperatures (apart from at locations very close to the fire itself) to significantly exceed the sprinkler bulb temperature.  So in general the curtains will be subjected to relatively low temperatures within a building fitted with sprinklers, so there is no need to consider thermal shock. 

Please give us some idea of your experience of dealing with Building Control or the Fire Service: I can imagine that they will often query the use of automatic fire curtains across an escape route. What has typically been their attitude towards the use of fire curtains in lieu of passive construction?

The usage of a fire curtain across rather than beside an escape route probably provides the most difficult challenge to obtaining the approval of such Authorities.  Generally whether this is accepted or not tends to depend upon the Authority concerned and just how much experience and knowledge they have of fire curtains, because fire curtains and their associated standards are relatively new. If you are in discussions with an Authority where fire curtains are not particularly well known it can be quite difficult to get approval for this sort of application. 

I am not aware of any applications where we have put forward this kind of proposal and had it rejected. I don’t know what experience consultants have in putting these kinds of proposals forward before starting talking to manufacturers.

Are there fire-resisting treatments which can extend the life of these products?

The fabric of a curtain (whether used as a fire or a smoke curtain) tends to be treated to avoid the shedding of fibres during the rolling up and rolling down of the curtain during normal testing. This treatment is not intended to provide protection in case of fire. Some curtains have an intumescent coating, but I have got no experience of intumescent coatings: Colt doesn’t offer a curtain with that type of coating, so I can’t comment on their life and reliability of these coatings.

Should the audibility of fire warning systems be taken into account?

Generally we, as a curtain supplier, wouldn’t consider the effect of a curtain being lowered on the audibility of a fire alarm system, but a fire alarm system supplier might have to.  Generally a fire curtain will provide no more attenuation than a fire door. 

Please explain the issue of the untenable zone to BS 8524 insofar as it exceeds the curtain deflection zone 

Generally the curtain deflection zone itself is taken from the test results of the fire curtain, so when the fire curtain is fire tested, the deflection is measured and that is used then to calculate the untenable zone.  So we take the deflection zone plus a small fixed non-tenable zone (at least 250mm) to give us the total untenable zone from the axis of the curtain through to the usable part of the escape route. 

What are the issues with harmonisation of the EN standard and EN 16034?

The issue is that there are already a number of other harmonised European Standards for fire doors and there is some concern that there are clashing requirements between EN 16034 and these other standards. There are committees looking at that at the moment and trying to resolve the clashes so that the standard can be modified and harmonised as soon as possible – unfortunately I can’t tell you when this process is going to be completed.

How do you calculate the depth of smoke curtains in an atrium?

Generally in an atrium smoke curtains are used simply to separate the balcony from the main part of the atrium.  It is very rare to divide an atrium into two or more smoke zones with smoke reservoir curtains, so there isn’t a normal design method to calculate the depth of a smoke curtain. It is simply that the curtain descends from the ceiling to the floor, on each level.

Is there an easy way to visually identify whether a smoke or fire curtains has been installed?

There are two general ways of identifying this. First of all, if it doesn’t have side guides it is definitely a smoke curtain and if it doesn’t descend to floor level it’s definitely a smoke curtain.

If it has side guides and descends to floor level it is probably a fire curtain, but the only way you can be totally sure is that a smoke curtain will have a CE mark on it to EN 12101, so you’d have to look for the CE mark to be 100% sure. 

Can fire or smoke curtains be mounted at an angle?

The answer to that is yes, but it depends upon the manufacturer exactly what angles they can provide.  Certainly there are horizontal and angled curtains out there, and there is no regulatory requirement that prevents use of angled or horizontal curtains.

Are fire curtains ever used to omit the need for a permanent physical wall for a protected lobby?

The answer to that is yes. We have seen a number of applications, particularly between say, a two storey entrance atrium and a lift lobby or stair lobby behind, where a fire curtain has been used to protect the lobby.

How do we assess competency of installers and what should we ask for in signing off an installation?

At the moment there is no specific method of assessing competency of installers, particularly for fire curtains.  Generally you might look at the reputation of the manufacturer and the installers.  If you are using a manufacturer to both provide and install the curtain, then if you are using a reputable manufacturer you would expect their installer to be competent as well.  Some installers might have been certified to the old PAS121 standard which can also be a guide to competency.

If you are just using a general installer to install a curtain which has been bought supply only, then there is no specific means of assessing competency, it just comes down to checking the installation thoroughly to make sure that has been done properly.

How long a time should be allowed for multi-position deployment for the curtain i.e. the maximum holding time for the curtain above 2m?

There is no specific limit for this. What is generally done is to ensure that as well as having perhaps a timer delay, you also have a heat detector mounted close to the top of the open zone, so that if it becomes hot there the curtain will drop, regardless of the time.

Paul Compton Paul Compton is Technical Director for Colt, experienced in smoke control, HVAC, solar shading and louvre systems.

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Topics: Fire Containment, Smoke Containment, Webinar, Curtains