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Each issue, the ECA’s Technical Services department answers a selection of members’ most frequently asked questions – providing expert guidance and tips. This issue, the focus is on fire alarm systems (BS 5839-1 and BS 5839-6)


Fire alarms


Q|Is BS 5839-6 a legal document, and recommendations?


am I forced by law to implement its


A|Firstly, BS 5839-6 is only a code of practice, and on its own it has no legal


standing. BS 5839-6 is one way of complying with the Building Regulations and, to some extent, it is accepted as the best way to achieve compliance. If a project specification calls for BS 5839-6 and a contract is placed for the work to be carried out to this standard, BS 5839-6 becomes enshrined in the contract and therefore becomes a legal requirement under contract law.


Q|Battery-powered detectors – can they buildings?


to recognise the existence of these units for use by owner-occupiers of existing single storey dwellings. There are warning provisos regarding the use of Grade F systems.


which has a number of flats. Both be used in new and materially altered


A|No, these are listed as Grade F systems in BS 5839-6. They are there in order


Q|I am rewiring two houses, one of


have battery-only smoke alarms at the top of the stairs. Do I have to add additional units, supply them from the mains and link them together?


buildings, although they belong to the same person. One is the single-family dwelling of the owner of both dwellings and the other is a small two-floor rented ‘house in multiple occupation’ (HMO) containing four flats. With the single-family dwelling, it is the occupier who will dictate the system grade or category of any rewired smoke alarm system. He has


A|To answer the question, we need to deal with these as separate functional


64 ECA Today May 2011


no legal obligation to have any form of smoke alarm in his dwelling but may wish to purchase an upgrade, if only for his own sense of safety. Since this is an existing house, a BS 5839-6 Grade F LD3 system would be acceptable. Please refer to the section on grades and categories relating to Grade F LD3 systems. Where the structural fire precautions are of a lower standard, a Grade D LD2 system should be recommended. Remember, all decisions on what is to be installed are the occupier’s. In considering the two-storey house, HMO,


with the four rented flats, this will be subject to a fire risk assessment provided by the landlord (the responsible person). The landlord has a legal duty of care to his tenants to ensure that they are kept safe from harm due to the effects of fire within the rented property. In this existing building, the minimum, subject to the outcome of the fire risk assessment, would be a Grade D LD3 system in the common areas and, if there are two or more rooms in the flats, a Grade D LD3 system in each flat.


In existing HMOs where the structural fire precautions are of a lower standard, the fire risk assessment should call for Grade D LD2 systems in both the communal areas and each flat. In the event that the flats have only one room, then there is no requirement in BS 5839-6 for a smoke alarm. However, it would be prudent to recommend to the landlord that, as a minimum, a battery or mains-powered smoke alarm should be installed in the room to cover the sleeping risk. These do not need to be connected to the communal system.


Q|BS 5839-1 recommends that detectors should not be sited less


than 500mm from walls and beams, and BS 5839-6 recommends that they should not be sited less than 300mm. Which one is right?


A|BS 5839-1 is primary concerned with commercial buildings where corridors


are more than 1000mm wide. As BS 5839-6 deals with domestic


dwellings where corridors are less than 1000mm wide, it is not practical to have detectors 500mm away from walls as this might not be achievable. Therefore, 300mm is acceptable in domestic dwellings.


Q|Do Grades C, D and E systems need to be wired in fire-resistant cable?


A|These grades of system need only to be provided with general cables, which


are suitable for the voltage and current being used by the system. Only Grades A and B require fire-resistant cables.


Q|BS 5839-1 says that for reasons of electrical safety, the mains supply to


all parts of the fire alarm system should not be supplied via an isolating protective device (such as a circuit-breaker). BS 5839-6 on the other hand, says that the circuit serving the fire detection and alarm system should preferably not be protected by any residual current device (RCD). Which is right?


A|Dedicated circuits are required for Grades A, B and C systems, and


BS5839-1 systems, so the use of an RCD is


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