Electrically Powered Sliding Doors as MOE

[Dragon100]

Hi - a newbie joiner here!  Sorry if this is a stupid question to you guys but we are a little stumped and overwhelmed with different guidance books being thrown at us so wanted someone's experience on these...

We audited an office block recently - 7 storeys with occupancy around 350 (normally).

2 escape stairs including 1 firefighting stair plus firefighting lift.  Dry riser in firefighting stair.

At ground floor, there are 2 main exits.  One is the normal entry point (which has electrically powered sliding doors - but no pivot swinging door adjacent) and a pivot swinging door at the rear closer to where the two stairs discharge. The pivot swinging door is fitted with thumb bolt but also in interfaced with fire alarm, fails safe when electricity lost, and has Type A green break glass unit adjacent (within 2m).

The electrically powered sliding doors DO 

• automatically open within 3secs of fire alarm actuation and
• fail safe in open position when power fails (it also has battery back-up unit nearby).

The electrically powered doors DO NOT

• have a pivot door adjacent opening outwards or
• automatically swing open when force from inside the building is applied/

Now the query we raised is 'why doesn't the sliding doors also have a Type A GBGU?'... the fire strategy document and FRA don't mention the sliding doors needing the Type A GBGU either.

Also, the fire strategy does not mention the electrically powered doors being an escape route - but the door is signed as a means of escape.

Our understanding was that all electrically powered doors along escape routes (and electronically secured doors) should have a Type A, GBGU unless in correctional facilities or others where they may be used inappropriately.

We have looked at BS7273-4.  Table B3 suggests 'Any' category of actuation can be accepted in offices for sliding electric doors.  Does these mean that the Type A GBGU is not required as it is an office occupancy?  

If the fire alarm actuates and the power goes down (unlikely I know) and the doors do not open for some reason, would the introduction of a Type A GBGU allow the doors to automatically open when the frangible element is broken, or would it just allow occupants to manually slide the doors open?  

Any thoughts / experiences with these would be much appreciated.  Our concern is 350 trying to use the one doorway at the rear of the building may become a bit cosy!  But the main sliding doors may not be suitable as no GBGU.

[Messyshaw]

Hi Dragon 100 & welcome to the forum. Where have you been?!!

The set up you describe sounds similar to many offices I have seen and from what you describe, it sounds suitable & sufficient - EXCEPT not having a override on the from sliding doors. If the doors can be opened by physically pulling them, that may be acceptable, as long as the force required to force them apart is within certain limits (20 or 30 Newtons I think - I can never remember - see ADM).

If that is not feasible then an override is absolutely necessary. You mention that in correctional facilities Green Break Glass Units (GBGUs) are not required. That is true, BUT there still need to be an override for electrically locked that only staff can operate by a key. I worked applying fire safety in secure mental health units including forensic MH units. All operated a key override system on locked doors and it was a constant grumble of mine that during an audit of training, I would ask staff to present their keys for inspection, and so many didn't carry them!!!!!

Many buildings where I work in now have high value contents, so we need to balance the physical security with compliant escape routes

Across our estate we use hundreds electrically locked pivoted doors and sliding doors on escape routes. Because of the valuable contents, the electrically secured do not fail safe - they fail secure. OK this is unusual, but I think you will agree it would be daft for a secure building -for example a bank or safety deposit vault - to open all its outer doors in the event of a power cut!

But ALL of our electrically locked doors are fitted with overrides - without exception. It is inconceivable  to me for any locked door (whether mechanically or electrically locked) on an escape route not to be fitted with an override.

Where doors are expected to take considerable traffic in an evacuation, but are not designed to fail safe, the GBGUs are tested weekly as a mitigating measure for this variation.

As far as what the GBGU does in respect of sliding doors, in your case being an office with few members of the public, it may well be possible for the GBGU to operate and allow the doors to be slid manually apart. Staff training and appropriate signage may suffice.

Or you could adopt a management system where perhaps a receptionist, or nearby member of staff, will immediately check the sliding door has opened when an evacuation has been triggered and if not, that staff member will operate the override and pull the doors apart before other staff arrive.

 

So to sum up, don't forget that guidance is just that. Any measures in a British standard will usually be compliant, but you can adopt a variation to whats on offer in a BS or ADB, as long as you achieve at least the same level of safety.

Personally, I would be unhappy with sliding doors anywhere without a GBGU that operates them to open, or allows them to be opened easily - UNLESS they can be manually opened with ease and without delay without the use of an override and are adequately signed

[Dragon100]

13 hours ago, Messyshaw said:

Many buildings where I work in now have high value contents, so we need to balance the physical security with compliant escape routes

That is such a great answer - thank you for taking the time to explain all these points.  

It is really interesting that you mention the balance of physical security and fire escape routes too...

The tenants in the building collared us whilst we were doing the walkaround - they are worried (understandably I guess) that when they perform their fire drills, the building is obviously left empty...but all the lovely electronic security they have in place such as secured doors which only open normally with fobs, and the perimeter doors all open nice and wide...and is very inviting for people to just walk in and grab stuff!

In your experience, is there a time period after all the doors have pinged invitingly open when all the doors will re-set and close / secure?  I am not thinking about the internal doors as these may be needed by the fire service crews to do their job, but I am more thinking of the great big sliding glass doors at the front of the building?  When we looked at the cause and effect certificate issued by fire alarm engineers, it just shows the interfacing of the doors with the alarm, but they appear to only close / re-set when the alarm is physically deactivated by hand.

[Messyshaw]

It is usual practice for electically locked doors to open/unlock via an interface from the fire alarm system, and as you say, they can only be re secured when the panel is reset.

Most of our final exits are not released by the fire alarm so can be locked as the last person leaves.

But where we have final exit doors that remain insecure, we post staff at them to maintain security. 

I havent heard of doors re securing after a set time, but as long as they can be overriden from the inside I am sure it's technically possible and compliant 

[Dragon100]

Thank you for your advice.