Use of extract fans to achieve purge air requirements for gas cookers
If the kitchen has no external walls, the ventilation provision (background and purge)
should be via an intermittent mechanical extraction fan. The extract fan rate should
be a minimum of 30 l/s where the fan is located above the hob and 60 l/s if the fan is
located elsewhere in the kitchen. Intermittent extract can be operated manually
and/or automatically by a sensor (e.g. humidity sensor, usage sensor, etc.). In
kitchens, any automatic control should provide sufficient flow during cooking with
fossil fuels to avoid the build up of combustion products.
Any automatic control should provide a manual over-ride to allow the occupant to
turn the extract system on.
The fan should have a 15 minute over-run facility. In rooms with no natural light the
fan may be controlled by the operation of the main light switch.
If the extraction is via a cooker hood, the cooker hood should be installed paying due
regard to both the hood and cooker manufacturer’s installation instructions.
Mechanical extract terminals and extract fans should be placed as high as
practicable but preferably within 400mm of the ceiling.
To ensure good transfer of air throughout the dwelling, there should be an undercut
of a minimum area of 7600mm2 in all internal doors between the internal kitchen, the
adjoining room and outside air above the floor finish. (This is equivalent to an
undercut of 10mm from a standard width 760mm door).
... TB005
