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.) |