smoke ventilation

[bevfs]

hi all,
is it requirement that an audible alarm is raised when the smoke vetilation is activated?
ie communal stairwell- residential flats (or any other senario)

[kurnal]

Depends on the reason for the smoke ventilation and the evacuation strategy for the building.

In most purpose built blocks of flats the ventilation system will not generate an audible alarm because most flats are designed to a stay put strategy. In these buildings the purpose of the ventilation system is to keep the staircase free of smoke to enable the fire service to access the flat of origin for fire fighting purposes. There will not normally be an audible fire alarm system in the communal areas, each flat will have its own stand alone domestic system.

In large retail or warehouse buildings or basements, where the ventilation system is used for example to compensate for extended travel distances, the ventilation system is designed to work in conjunction with the fire alarm system to ensure that the means o f escape remains tenable throughout the evacuation phase.

[bevfs]

yes i understand,
the point is a communal area (m of e)could be at risk smoke has been detected and the vent has operated
no person (in their flat/apartment) will be aware of this as potential as no warning has to be given.It this seems
to be wrong as ie 1 route in/out protected, their has been a breach in either the compartmentation,or a hazzard has been
brought in ie plumber hot works in services cbd smoke logging the communal m of e,albeit venting  smoke,with nobody inside their flats aware,apart from the plumber running aroud frantic

[Golden]

Bev, from what angle are you approaching this? Are you a concerned resident or someone that works for a landlord for example?

[bevfs]

just my own personnel thoughts on an accepted standard.Premises relying on high degree of compartmentation
and risk seesments passing off premises safe, where compartmentation has has been breached by tradesmen.Just having an "early warning" or a heads up on whats going on in the  m of e ,even if only linked to the smoke vents,as well as compartmentation would be a better stance.The term "having all ones eggs in ones basket" springs to mind
but only my personnel thoughts your honor

[Golden]

OK that explains a bit more. Firstly I'd like to say that fire spread between flats is rare, I know we have the Lakanal House example but even in that instance the compartmentation (faulty though it was) contained the fire for approximately one hour. My second point is that we have to consider that evacuating residents into a staircase that is full of smoke is a bad idea - its much better to keep them in a flat and let the FB come in and extinguish the fire and having a smoke ventilation system will facilitate those actions plus keep the heat in the area reduced to restrict the chances of fire spread or even backdraught.

It is the assessors job to look for breached compartmentation, generally in blocks its reasonably easy but there are exceptions maybe where false ceilings have been put in or in the case of unusual designs such as the scissor blocks like Lakanal. It is more common to find problems in newer blocks and often these can be difficult to find where trades have carefully hidden their shortcuts - particularly if you've only been commissioned to do a 'type 1' inspection - but a good assessor will know where to look for the tells. Having attended plenty of high/medium/low rise fires I've had more problems from people evacuating en-masse, or in one case where a well intentioned MoP battered a flat entrance door down in an attempt to try to save the occupant, than I have from fire spread from one flat to another.

[wee brian]

why tell people there is a fire, if you don't want them to do anything.

most flat fires start and finish whilst many of the residents are asleep. better to leave them alone. (they would ignore the alarm anyway)

[alonso]

hello everyone first post. I'm a fire alarm engineer in the trade for 10 years who's done some work on smoke vents when no-one else wants to know! And I'm interested in this.

I have a question - if the s.d. detects smoke and operates vents but doesn't sound alarms then what happens next? does the smoke vent system dial to an arc or caretaker who investigates the alarm? or does it just vent the smoke and wait for someone to leave their flat, notice the smoke and call the fire brigade?

cheers!

[Golden]

Alonso - you are correct as it just vents the smoke, the theory being that someone will notice the fire and dial 999. Its not really been a problem as unoccupied flats rarely catch fire however you are also correct in assuming that a fire may grow in intensity in a flat if nobody raises the alarm.

[Mike Buckley]

There are other factors that need to be considered.
1. The staircase and MOE should be clear of combustible materials  Hence it is unlikely that a fire will start in these areas.
2. if there is no communal fire alarm system there must be adequate fire separation between the individual flats which will mean that a fire is most likely to remain inside the flat. If the flat is unoccupied and all the windows etc are closed the fire may well snuff itself out if not he fire is more likely to break out through the windows where it will become very obvious.
3. The smoke ventilators should ensure that the escape routes from the other flat remains relatively clear.

An issue that does need addressing however is a practical one. If the automatic detection operates and opens the ventilator what indication does it give, so that someone knows about it and they can come and close the ventilator?

[AnthonyB]

An issue that does need addressing however is a practical one. If the automatic detection operates and opens the ventilator what indication does it give, so that someone knows about it and they can come and close the ventilator?

Most properly installed vents I see either have:
- A purpose designed control panel provided by the vent manufacturer with the capability to have detectors directly connected; or
- Simple actuators that are triggered by output/relay from an L5 (not L5/M if done right) fire detection system

In either case there will be a visual and audible indicator at the panel that the system has triggered and thus the vents open.

[Mike Buckley]

The reason I mention it is I was in a team which did an FRA for a Grade 1 listed building of museum status. This had smoke vents in the roof space, these should have opened on activation of the fire alarm. They did not operate because the staff had disconnected them because there was no method of closing them except going up into the roof space and closing them manually. Access to the roof space was difficult and the staff had short cut this to save them going up into the roof every week following the fire alarm test!

As I believe Albert Einstein said, 'Only two things are infinite, the universe and human stupidity, and I'm not sure about the universe'

[Golden]

Mike although I agree fully with the point you have made my responses to this thread were based on the initial question that I believed referred to un-monitored vents in residential blocks. In my experience these can have varied control and indicating equipment - from zero to a fully monitored and controlled system although most I've found tend to be nearer the zero end!

Where vents are provided in commercial buildings, particularly something such as a grade 1 listed museum where any rain ingress may cause more damage than a fire, I'd expect them to be fully alarmed and staff to be able to remotely reset - although this is symptomatic of many fire protection products which are specified and installed without a thought to the end user, and often without the end user not even knowing they are present until a FR assessor turns up and asks them when they were last tested!

[bevfs]

yes thank you for pulling the thread to my original point.
ie fault overload in mains electrical cbd,causes fire, smoke vents stay shut on m of e.Having a small indicator light on a small smoke vent panel,in communal area,will alert nobody and is good for nothing. (level1 fire risk assesment carried out non invasive-service holes knocked thru compartment walls etc,so poor structural compartmentation not 100% as nothing is in life)It surely should be an audible alarm on the communal to alert relevant persons,as a previous response states,communal areas m of e ,have a  very low risk of any fire ,so few or no false alarms,so we have derivedminimal chance of a fire in the m of e .So having a  heads upIf anything happens as they say forewarned is to be forearmed
On which i will add the question will a smoke vent fail safe to the open position,in the event of mains power failure?(this is surely a mandatory?)

[AnthonyB]

If the compartmentation has been damaged, repair the holes - the last resort is fire warning systems as they would have to include sounders in the flats to be of use at all times, would be a nightmare to service, would still be ignored and subject to vandalism - there is a reason the guidance & Building Regs don't require them & it isn't to upset fire alarm installers!