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Fire Alarms in Small Office Building


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I have a small office building on site which is around 60 sqm with 2 floors, 5 offices a kitchen and external boiler room.

Normally there will be 4 office staff in the building who are all familiar with the lay out which has 1 exit.

My question is do I need to install some kind of fire alarm system or would hardwired interlinked smoke alarms suffice?

Thanks in advance.

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As you are considering a commercial premises, interlinked smoke alarms will not suffice as they are for domestic premises. (BS 5839 part 6) You need to consider a BS5839 part 1 system and I would suggest you would need at least a category M system and could be more depending on you Fire Risk Assessment.

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Because it's over one floor and split into several rooms, "manual" or non electrical means of alarm (shout's, gongs, etc) are unlikely to be suitably audible.

Most fires in single company occupancy buildings during working hours are likely to be detected by sight and smell (you may smell a really small fire quicker than it would activate a detector) or even sound and so the minimum fire alarm requirements in Building Regulations and BS5839-1 (Fire alarm standard for non-domestic premises) is a system of manual call points and alarm sounders.

Automatic detection is only required where there is a risk of a fire developing undetected for some time such that it could affect escape and thus life safety and even then is applied in layers - detectors for specific risks/purposes (L5); for escape routes (L4); for escape routes and adjoining rooms (L3); escape routes and adjoining rooms plus specific areas of risk(L2); virtually everywhere (L1).

The higher categories (L2, L1) are usually only needed for sleeping risk, healthcare, fire engineered buildings, etc - some installers will try and put you detection in everywhere despite there being no legal basis.



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It would also be worth checking with your insurers to see if they have any specific requirements.

The last thing you want is to go for a Category M which as mentioned would meet the legal requirements only for your insurer to say its not adequate enough for them to insure.

You should also follow the guidance and recommendations of your FRA.

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  • 3 years later...

Hi all,

I have a similar situation as described, but my office is around 100sqm single floor, but with an office (17sqm) laboratory (17sqm) and Meeting room (20sqm) (20 people max) that also has a tiny area to prepare snacks (no cooking utensils, besides a kettle) 

How many fire alarm sounders is required??

by reading some of the legislation i cannot find any specific number or anything saying one per room or similar.

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Sufficient to achieve 65dB throughout except to areas of limited extent, cupboards and similar, rooms under 60 sq.m. can also have a lower sound pressure of 60dB.

You should be using a qualified fire alarm system designer and installer who will look after this for you and ensure your system meets BS5839-1:2017

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Guest jackie

we rent out a house. currently the 3 presidential flats all comply. the front of the house is a small barber shop which is only 12 ft by 12ft one room only. does this require smoke alarms etc 

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If it is suitably fire separated from the flats then it can be looked at in isolation and wouldn't need any fire alarm or detection being a single room as the occupiers would easily detect a fire themselves and verbally raise the alarm.

If it isn't then a fire alarm system covering both the shop & residential areas may be required.

Both the common areas of the flats and the commercial unit are subject to the Fire Safety Order and require a Fire Risk Assessment. Also it sounds the house conversion to flats could fall under section 257 of the Housing Act 2004 if:
1. the conversion did not comply with the relevant Building Regulations in force at that time and still does not comply; and
2. less than two-thirds of the flats are owner-occupied.

Depending on location it may also require licencing as a s257 HMO if your council operates an 'additional licensing' scheme.

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  • 2 months later...
Guest Pete

Hi there,

I own a small restaurant.  It is primarily set in 2 zones, the front part of the restaurant approx (30sq/m) has a small dining room, 30 sq meters and  an open kitchen that caters for 30 diners.  There is then a corridor to the prep kitchen in the back, an area of 15 square meters.  In between the two main areas of the restaurant are two bathrooms.

The space overall is approximately 70 sq meters.  We currently have two Fireangel Pro Wi Safe smoke alarms linked together, 1 in the front part, one in the rear. In such a small space is anything else required?  We've had mixed messages from building control, in one email they have approved our current system, in another have suggested we may require a fire panel.  Now with everyone furloughed, we haven't been able to get in touch!

Any help would be greatly appreciated! 

Thank you!


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If an existing operating premises and not a fit out in progress it's outside the jurisdiction of Building Control and is a matter controlled under the Fire Safety Order enforced by the Fire Service. Under this you, as the Responsible Person are required to determine your requirements by a Fire Risk Assessment, which as licensed premises should be written regardless of the number of employees.

Fire Angel devices are for domestic premises only, although in certain circumstances may be mitigated in a Fire Risk Assessment if of the dual power supply type (mains and battery).

The first requirement is for raising the alarm throughout the premises if someone discovers a fire - in really small premises this can be verbal (taking in to account background noise) if a shout could be clearly heard throughout the premises. If not then some form of enhanced warning is required - this would be an electrical fire alarm system to BS5839-1 Category M, comprising manual 'break glass' call points & alarm sounders linked via a control panel.
You don't need automatic fire detection in most non sleeping premises unless the layout or risk requires it (or you choose to for property protection purposes which isn't a legal requirement) although in your case you my need some coverage - only a site visit as part of an FRA can determine this unless you have decent accurate floorplans.


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  • 6 months later...
Guest Office building

We have a multi-floor office building.  We were told we need a hardwired fire alarm system with at least one alarm in every room.  Can we just have battery operated fire alarms or does it need to be hardwired?  Thank you.

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You require a fire risk assessment by a competent person as required by fire safety legislation (irrespective of size of numbers of occupiers) which would give you a detailed requirement.

Such an assessment would require an electrical fire alarm system designed and installed in line with BS5839-1:2017 to a minimum of Category M, comprising manual call points at storey and final exits and suitable alarm sounders throughout to give an audibility level of 65dB (60dB in small rooms under 60sq.m and stairwells)

Your fire risk assessment would determine whether the layout of the premises required Automatic Fire Detection in addition as part of the system and to what category you require - more detail here https://www.safelincs.co.uk/a-summary-of-the-bs5839-1-2017/

Equipment can be hard wired using fire resistant cabling or wireless linked:


The use of residential/domestic detection, even if mains supplied, would not be suitable. Self contained detectors would be useless as they would only alert the room they are in (the alarm must sound throughout the whole building) where the occupants would see it themselves first, but be unable to raise the alarm due to lack of call points. Battery only detectors are not legal for use in workplaces as only having a single power source.

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