Basement transformer extract room
Basement transformer extract rooms contain high risk equipment, such as oil immersed electrical plant, and require entirely independent fire rated ductwork – BS 9999:2008, clause 33.4.7.
- Ductwork should be impact resistant to BS 5669 and BS 9999:2008
- Electrical transformers and switchgear are at particular risk and require an entirely independent ductwork system.
In the diagram
Transformer room extract duct (shown ) must be suitable for ventilating the transformer room to atmosphere, rated for stability and integrity to resist fire from inside (Type B). Insulation is not required in the first compartment.
Where the duct goes through the lobby (shown ) it must maintain stability, integrity and insulation, for the same period of time as the compartment through which it passes to the outside.
In some circumstances, insulation requirements may be waived or varied by the regulatory authority if there are no combustible materials within 500mm of the duct – BS 9999:2008, clause W.4.
All fire rated ductwork and penetration seals must be tested to BS 476-24/ISO 6944 or BS EN 1366-1 and classified in accordance with BS EN 13501-3 by a recognised NAMAS/UKAS accredited laboratory.
Note: Final approval must always be obtained by the local building control officer/fire department prior to commencement of construction