Sally H

Hello David It is true that Table 4 at 3.20 of The Building Regulations 2010 Fire Safety Approved Document B states the maximum number of persons who can be accommodated by a final exit door of 1050mm width is 220. However, what if this exit is blocked by fire? At 3.21, 'Calculating exit capacity', the regulations note that 'if a storey or room has two or more exits, it has to be assumed that a fire might prevent the occupants from using one of them'. This is true of a room with only one exit. If this one and only exit is blocked by fire, what are your contingency plans? Furthermore, even if the exit is not blocked, to assume the maximum number could be safely accommodated is taking a huge risk; depending on the nature of the fire, a panic situation could develop, with a mad rush of 220 people to the door and the possibility of some being crushed. Have you thought about creating an additional fire exit via a window? Kind regards Sally

Hello Lauren For fire exits, the width is the most important factor, and this is determined by the number of people who are likely to be using a particular exit. Current Building Regulations (Fire Safety, Approved Document B, 2010) specify a minimum width of 750mm for a final exit door, to accommodate a maximum of 60 people. As a matter of interest, the minimum standard dimensions for a fire escape roof window (as opposed to a door) are 660mm by 1180mm. Height wise, your door is OK; but it is too narrow for its purpose.

When retrofitting intumescent / smoke seals to an existing fire door, both vertical edges and the top horizontal edge of the leaf must be sealed. It is not usual to seal the threshold. In respect of double doors, the rebate alone is insufficient to prevent the ingress of 'cold smoke' around the door edges in the early stages of a fire. As a fire develops, and as noted in the ASDMA Best Practice Guide to Timber Fire Doors, the meeting edge between double leaves is particularly vulnerable because relatively small differential movement in the door leaves through exposure to heat and flames will greatly increase the possibility of integrity loss due to gap formation through distortion. The role of the intumescent seal is to control this distortion; the Intumescent Fire Seals Association (IFSA) guidance on the upgrading of joinery doors notes that fire doors normally fail by distortion, rather than burn-through. The IFSA guide further notes that seals must provide low closing friction to prevent the seal from inhibiting the door from closing effectively and fully.

It would not be acceptable practice to use your fire exit as a goods entrance. This is because the final exit door(s) and escape route(s) through a building must be kept clear at all times. You mention that this is the only escape route so the risk would be that goods are being delivered/unloaded from a vehicle or perhaps taken into the building when fire breaks out elsewhere in the premises. The one and only route and exit would then be blocked and people would not be able to evacuate swiftly and safely. It is fine to allow staff to enter through the doors with a key; but to exit the building the doors should be fitted with emergency push pads, so that no key is needed in order to escape from the building in an emergency/fire situation.

Current benchmark design guidance recommends that stairways in blocks of flats need to be enclosed in fire-resisting construction to minimise the risk of flames and smoke entering the stairways while they are being used to escape; this means that the doors opening off the stairs at each landing must be capable of providing 30-minute fire resistance (FD30) and be self-closing. (Local Government Group "Fire safety in purpose-built blocks of flats"). It is not usual for such communal fire doors to have handles/latches.

If a fire doorset with intumescent seals in the grooves of both the door and the frame is subjected to the furnace test under BS 476: 22, the pressure exerted by the seals might be so excessive as to force the door open. This advice is from the Intumescent Fire Seals Association (IFSA), who recommend that one of the grooves be filled in. It is possible to purchase an empty plastic seal casing, which can be used as a filler; alternatively, for a timber doorset, a hardwood filler for the door or hard or softwood for the frame would be appropriate. For further advice and technical guidance visit: www.ifsa.org.uk