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FIRE SAFETY => Fire Risk Assessments => Topic started by: Messy on March 23, 2017, 04:09:01 PM

Title: Ventilating Difficult Staircases - Slighly Out of My Comfort Zone
Post by: Messy on March 23, 2017, 04:09:01 PM

I have recently carried out a FRA in a large office building with 6 lobbied staircases of 10 floors. I am trying to determine control measures for staircase ventilation. This would not be my 'specialised subject' if I were to appear on Mastermind so I am struggling a bit!

Findings:

Staircases 1 to 4 are pressurised. No issues here
 
Both of the other staircases (5 and 6) have what should be openable windows at the head, but no obvious inlets anywhere lower down. Both of the supposedly openable windows are secured and the occupier wants them to stay that way. This requirement is not negotiable

Staircase 6 (with no effective ventilation at the head of the staircase) is also a fire-fighting staircase and the fire-fighting lift is used for the evacuation of disabled persons

Meanwhile, I cannot find any ventilation in any staircase lobby on any floor or any staircase. It will be very difficult to install retrospectively

Control measures:

Lastly - and to throw a spanner or two in the works- the building is Grade 2 listed - and of course the staircases are full of heritage features. It is not possible to fit roof mounted AOVs without question. The fitting of bottom hinged drop down window AOVs might be tricky as significant changes to the historic windows will be required. I honestly doubt this would be acceptable to the occupier or Building Control. The RP does not want English Heritage or BC informed at this time.

Frankly, I haven't got a clue how to vent the staircase lobbies - or even if I need to. Travel distances (two way) to staircases are around 30 to 40m, so not that excessive, and the premises is fitted with an L1 AFD system


My web search for reference material has thrown up loads of info on residential premises but none on commercial premises. And my copy of BS9999 is elsewhere and I can't get it until Tuesday as I am enjoying some time off (as you can see!!! ::))

So where do I start?

I know I need to get ventilation on each of the two non pressurised staircases - with the fire-fighting staircase as a matter of priority
But I am not sure if the lobbies need to be ventilated as the TD doesn't seem too bad
Lastly, I am not sure where to look on the web for guidance

Any ideas????

Title: Re: Ventilating Difficult Staircases - Slighly Out of My Comfort Zone
Post by: Phoenix on March 25, 2017, 10:39:29 PM

Hi Messy,

If the building is in England or Wales then there is no general requirement to ventilate the staircases in commercial buildings.  Normally, only firefighting stairs in new buildings need ventilation.  With six staircases I would guess that at least two or three of them are firefighting staircases.  Therefore some of the staircases with pressure differential systems may be firefighting stairs.  Do these meet the recommendations for class B buildings (see page 19) as defined in BS EN 12101-6?  Routine service reports should verify this.  A 10 storey building will need firefighting lifts and this may help identify the firefighting stairs.  

If the pressure differential system was installed prior to 1998 then it will be installed to a different set of criteria.  Get back if this is the case.

Firefighting stairs or, indeed, any other stairs that have pressure differential systems would not have ventilation in the stairs or lobbies (it would be difficult to maintain a pressure difference if a staircase had ventilation - mind you, I've seen it!) so that would explain the large number of the unventilated lobbies.

Where there are some stairs in a building with pressure differential systems and some without there has to be a proven mechanisim for dumping the positive pressure from a pressurised stair before it reaches an unpressurised stair.  This brings me on to automatic opening vents in the envelope of the building.  For a pressure differential system to work, especially one involving firefighting stairs, there have to be at least two AOVs per floor that serve the space that is connected to the pressurised space.  Without such AOVs the open door requirement ("airflow criterion") will probably not be met - again, check routine service reports.

It would not be unusual if the service reports did not show this or even if there were no service reports.  Do check.

Ventilation in staircases would not be of benefit for means of escape and therefore not something that would normally be required in order to satisfy the FSO so I wouldn't worry about staircase 5.

Staircase 6 is a funny one.  Has it never had ventilation or has the ventilation been removed at some stage?  Is it definitely required as a firefighting staircase?  Article 38 only requires measures that have been installed to assist firefighters to be maintained, it does not require that they be installed.  So if ventilation has never been provided then you don't have to provide it now.  It does beg the question though, what use is it as a firefighting stair if it doesn't have ventilation in either the staircase or the lobbies?

Remember that it is not your job to bring the building up to a level that would meet today's standards for new builds.  If you're doing a fire risk assessment under the FSO then remember that relevant persons do not include firefighters.  You can advise them on how to provide proper firefighting facilities but they are not obliged to upgrade this element of the building.  I would suggest that your FRA should include full analysis of the requirements for firefighting facilities, bearing in mind the full set of circumstances.

Scotland has a slightly different take on ventilation in staircases as do a number of other countries.

In summary:    

Stairs 1 to 4	Check the servicing of the pressure differential systems.  Are all the AOVs working okay?  Have internal layouts changed (since system installation) that might vary the airflow paths inside the building?
Stair 5	Leave as it is.  No ventilation required.
Stair 6	Is it really required as a firefighting stair?  [Just because they evacuate mobility impaired people down the protected lift doesn't necessarily mean it has to be available for firefighters].  Even if it is required as a firefighting stair your client is not obliged to provide ventilation unless they, or a predecessor of theirs, has removed it.  However, it wouldn't be much use as a firefighting stair unless it does have some degree of ventilation.  (This still doesn't mean they have to provide it.)

Title: Re: Ventilating Difficult Staircases - Slighly Out of My Comfort Zone
Post by: Messy on March 27, 2017, 05:30:10 PM

 Phoenix

Many thanks for your reply. I really appreciate it.

A FRA review I have conducted has found that there are insufficient numbers of firefighting staircases for the area of the floor plate - This was accepted by Building Control when the building was refurbished many years ago as the usual requirements re the number of firefighting staircases was waived when taking into account:
    1) the Grade 2 listed status,
    2) the difficulty installing an additional internal stair,
    3) the difficulty upgrading an existing staircase to a FFing stair
    4) the proposed occupancy figures given at the time when the building was refurbished some years ago
    5) the L1 fire detection system

The recent FRA review shows that the current occupancy figures are satisfactory for the MoE, but are already much higher than those expected and provided for in the initial fire strategy submitted to BC. In addition there are plans to increase the occupancy figures further to a figure almost 3 x times greater than the original strategy.

Additional control measures are required to safely achieve this increase, including changes to the evacuation strategy and the introduction of a phased evacuation system.

I also intend to install AOV to stair 6 as its a firefighting starcase.


To confirm:

The building has 6 staircases with two of them firefighting staircases.  

The 4 x pressurised staircases installed before 1998

The 4 pressurised stairs - I have no issues with them at all. The servicing arrangements and records appear in order. However I would be interested to hearing about the pre 1998 standard

The  2 x non pressurised and non vented stairs both have manual openable windows (by a person physically opening them)  at the head of the staircase. According to the fire strategy - this is the agreed method of venting the staircases. One of the windows is at a very high level and would require someone to use a ladder to reach it - in the smoke??!!

The openable windows (including the one on the FFing stair) have been screwed and glued shut by the current RP. The RP will not allow them to be openable and has provided a good business case for this approach. There is no doubt that Article 38 has been breached in relation to the venting the firefighting staircase, but I believe a technical solution is possible which would satisfy the FSO and RP (if he can afford it). Its the listed status of the building that might be the headache here

There are no inlets or any other means of providing air inlet (including door opening) on both of the non pressures staircases - including stair 6 , the firefighting stair. I will look into this matter in more detail.


I will carry out some more investigations re lobby ventilation and get moving on seeking technical advice on a AOV for staircase 6

Thanks again

Title: Re: Ventilating Difficult Staircases - Slighly Out of My Comfort Zone
Post by: jokar on March 28, 2017, 12:21:31 PM

This seem a building that the local F&RS would be interested in, have you contacted them for advice?

Title: Re: Ventilating Difficult Staircases - Slighly Out of My Comfort Zone
Post by: Messy on March 28, 2017, 05:57:26 PM

Quote from: jokar on March 28, 2017, 12:21:31 PM

This seem a building that the local F&RS would be interested in, have you contacted them for advice?

Good God man, no!  I have got enough on my plate already without adding to my stress levels!

As you may recall Jokar, I was in such a team a while ago and have attended a number of premises to give advice and ended up requiring to serve a notice. I do not want that happening here.

The enforcing fire authority would have been involved in the building consultation process a good few years back and seemingly have accepted the BC's waived requirement in terms of the numbers of firefighting lifts. The building last received an audit about 8/9 years ago with no significant issues.

I am absolutely sure the RP is contravening Article 38 in terms of screwing the openable window closed at the head of the firefighting staircase. The RP is now aware and I need to give them time to respond with a plan of how this issue will be rectified. Immediately unfixing the window is not an option.

If I invite the enforcement team in for advice, I may promote a notice of FS deficiencies or even an enforcement notice. Such action is not required as the RP is keen to comply via an action plan that I will establish.

Title: Re: Ventilating Difficult Staircases - Slighly Out of My Comfort Zone
Post by: colin todd on March 28, 2017, 07:50:25 PM

At least Davey you are learning that its best to keep clear of your erstwhile employer's employees.

Title: Re: Ventilating Difficult Staircases - Slighly Out of My Comfort Zone
Post by: Phoenix on March 29, 2017, 01:26:02 AM

Hi Messy,

If the pressurisation system was put in before 1998 then it is unlikely to incorporate the features that are currently recommended for pressure differential systems in firefighting stairs as the standard at the time (the 1978 standard) made no references to firefighting stairs.  That standard allowed a number of options for air release from the floors including openable windows so you may not have the AOVs that would be expected on each floor for installations since 1998.

Stair 6 seems to be the one that needs sorting.  The whole point of providing vents in the lobbies and at the head of the stairs in firefighting stairs, as recommended, is to allow the smoke to leave via the lobby vent before it gets into the stairs, the vent at the top of the stairs usually acting as an inlet.  If there are no vents in the lobbies to stair 6 then I can't see there being much advantage to having a vent at the head of the stairs (depending upon circumstances it could draw smoke out from the fire floor which is just what you do not want with phased evacuation).  Are there openable windows in the lobbies?  Windows are vents.  Even if they are not the recommended size they can be reasonably effective at venting smoke. 

If there are no windows in the lobbies then think hard before you put a vent in the top of the staircase.  What will it achieve?  Remember, especially, that we don't want any smoke in the staircase during firefighting operations if the building has phased evacuation.  If it were simultaneous evacuation then it would not be so critical as most people should be out the building before firefighters start leaving doors to the fire floor open (though people with impaired mobility would need special consideration).

It would not be unusual if you had to develop some bespoke solution.  For example, if you put the vent at the head of the stairs (and it doesn't have to be an AOV by the way, a yellow 'break glass' box at access level to open it is recommended) you might accept that smoke might enter the stairs whilst there are still people on the upper floors on the basis that the staircase is treated as an accommodation stair.  That is, don't mark it up as an exit (but let people use it if they are able to and if they have some way to leave it at lower level - may be tricky if multiple occupancy) and discount it when calculating acceptable maximum numbers on each floor.

Also you should consider the point raised in 4.27 in ADB.  I like to start considering this issue in buildings less than 30m in height and I believe yours is about this height.  The management procedures it refers to could be direction away from the firefighting stair by fire wardens on each floor.  Again, the loss of a staircase would have to be considered when giving maximum occupancy guidance but the move to phased evacuation will give you plenty of extra capacity.

Bear in mind what I said about opening mechanisms, no need for AOVs, manually opening is fine with a yellow box at access level for the staircase vent (if you have one), not a person in BA up a ladder.