Air pressurisation system - stairway

[Paul1979]

Hi, please can anyone provide some guidance on following:

Office block - ground plus 4 upper floors plus roof space for AHU's and Air Con systems. Height is less than 18m.
Single stairway - protected at each floor with 2 door / lobby approach (2 x FD30s) including top floor.
No AOV system in stairway.
Occupancy, approximately 50-60.
Stairway is 1100mm clear width.

Whilst this is an existing building, I've looked at ADB (new) as guidance and 3.34 Access Lobbies & Corridors and the 2 door / lobby approach suggests that the current arrangement is adequate...I cannot see [correct me if i am wrong] any guidance in the HM guidance for fire safety in offices / shops.

But, we have unearthed an air pressurisation system within the stairway...we did not know this was here until we found the panel in the switch room during some refurbishments...it does not appear to be working and has definitely not been maintained...

The pressurisation system has never been picked up or requested in any of the previous FRA's [these have been performed by an IFE accredited risk assessor so we are comfortable that he is competent].

Do we need to worry about reinstating / maintaining the pressurised air system??

[Messy]

Assuming there's an AFD system (L2 minimum), simultaneous evacuation and cooperation between occupiers if multi-occupied, I wouldn't be too concerned about the pressurisation system not being available. This is conditional on the office building being in reasonable condition and no more than the low risk an office would attract (I did a job in a major fashion house 'office' to find a huge warehouse type fire loading of hanging garments).

Its always so difficult to comment blindly, but I would also consider:

6 monthly fire drills.

I would also conduct a detailed study of the lobby walls to make sure they are adequately fire resisting. I have never understood why two 30min doors are required to give a 60 min fire resisting capacity, but set in a 30 minute fire resisting wall!!! So I tend to feel committed to make sure the walls are in good condition if I can, or recommend an invasive inspection by a competent person

[Paul1979]

Hi Messy, thanks as always for the reply...appreciate that only limited information. Risk Assessment shows...

The fire alarm system comprises of a linked electrical fire alarm, with limited automatic fire detection, break glass call points and sounders in all communal areas, and a control panel at ground floor level.

[Note there is no specific confirmation of level of automatic detection, but I am assuming from FRA that this is only L3/L4 level as he says limited].

The fire alarm system operates a single stage evacuation system and is linked throughout the building.

But using ADB as a guide (assuming that construction is adequate) are we right in assuming that a pressurised system would still not be needed??

[Messy]

From what I am picturing, I would not recommend the pressurised system be re-establised

However I am concerned that the description of the AFD in the risk assessment is generic at best or perhaps vague at worse. Is the assessor using this description to hide a lack of understanding of what constitutes a particular BS5839-1 category or how to apply that standard here. Slightly worrying

If its a L4 I would be definitely be recommending L3 (detection in escape routes & rooms leading onto escape routes)- which in many cases for a building this size, may give almost total coverage

[Paul1979]

Hi Messy, thank you as always

[bernicarey]

With regards to pressurised stairways, I'll just chip in with my only experience of such a system.

About 13-15 yrs ago, I used to work in a 3 floor building (mainly office block with some 'technical facilities') that had been designed for around 300 but at the time the occupancy could be up to 450 on a really busy day.
We had a large central stairwell with airlock lobby onto each floor and as the building was helpfully a rectangular block, there was an emergency/alternative stairway in each of the 4 corners, also with an airlock on each floor.
THREE of these corner stairways, AND the central main stairway pressurised on activation of the alarm.
However, the 4th emergency stairway did not have the Fan system fitted.

The only reason I could think of was that the '4th stairway' unlike the rest, was the emergency egress from some very high security areas and their one way security doors to the stairway may not have had airlock lobbies.
But it was a very strange arrangement... So the criteria for the pressurised stairwells was somewhat of a Mystical art form...

I share Messy's concern over the vague phraseology used in the FRA regarding the Alarm System.

[Paul1979]

Thanks as always bernicarey...we chose the risk assessor on basis he was from a reputable company and he is on the IFE register for Life risk assessors...it is a bit of a minefield when choosing a risk assessor for the various properties we manage...

[Messy]

To be fair to the assessor, he or she may have avoided 'fire safety speak' to make the document more accessible for the customer. This is something I try to do as I get annoyed at those who try and build their professional status by being overly technical in their use of language.

But as with all communications, you need to phrase it in a way the intended reader will understand. In this case its the client AND any enforcement agency who need to understand your rationale when making that assessment

So why not say: " The fire detection system covers part of the building and has manual break glass call points. This is known as a BS5839-1 system to category L3 " - then everyone is happy