The BFCMA Guide (2001)says:
To start with all flueways should be checked monthly to assess the amount of deposits being created. The frequency of sweeping needed to prevent build up of deposits can then be determined. As a guide all flues should be swept before and during the heating season, and ideally at the end of the heating season to prevent tar and soot deposits having a corrosive effect on the chimney and appliance during the dormant period.
It is not recommended that the appliance is overi red [sic] or chimney fires are started in an attempt to
dean the chimney. Deposits of soot and tar will be greatly increased if unseasoned wood is burnt,
which can lead to chimney fires. Should a chimney fire occur, it is advisable to have your chimney
and appliance arrangement checked for damage before reusing the fire or heating appliance.
It is also good practise to check at least every year or two the exposed parts of a chimney, flashings
and terminals for signs of damage. Just like the outside of a house chimneys can suffer from the
wear and tear of extreme weathering.
If at any time smoke or fumes are apparent or suspected from the appliance, chimney or liner, seek
advice immediately from the installer or fuel authority in case there is a blockage or failure. Do not
use the fire appliance or chimney until they have been thoroughly checked for safety and soundness.
The escape of fumes can be dangerous.
Mechanical sweeping with brush and rods is the only method of cleaning recommended by British Standards, because materials other than soot can block flueways i.e. pargettng in old flues, mortar, brickwork, birds nests etc.
For this reason cleaning a flue using just chemical chimney cleaners or vacuum cleaning cannot be recommended as an alternative for correct chimney cleaning.
Sweeping brushes should be made from suitable bristle and be of the same diameter or area as the
flueway being swept, and be fitted with a ball or free running wheelboss on the end to prevent
scraping the flue walls, particularly at bends. Many chimney manufacturers give recommendations of
brush types to suit their systems. Use a qualified chimney sweep or member of NAGS (National
Association of Chimney Sweeps) who gives and inspection and sweeping certificate.
If there is doubt about the condition of a chimney, or an old chimney is to be put in use after a long
period of being un-used, his advisable to have it smoke tested. The purpose of the smoke test is to
discover if there are any major defects which can cause a leak of fumes through the chimney walls
during normal operation.
A smoke test should be carried out by a qualified person using the following procedure which is
based on the test described in British Standard BS 6461 Part 1. There is a different procedure for
smoke testing flues for gas fires. It is also recommended that this smoke test is carried out during the
construction of traditional masonry chimneys and on completion of all chimney installations.
It must be remembered that the purpose of the smoke test is to identify and deal with any faults
which would cause fumes to escape during the normal operation of the appliance and chimney. By
closing the bottom and top of the chimney during the test, the smoke generated by the pellet together
with normal barometric conditions will generate a positive pressure that would not be created during
the normal use of the installation, which operates under negative pressure i.e. sucking in air and
drawing the products of combustion up the flue.
The pressure created during the procedure is therefore more than capable of creating minor leakage
of smoke from either joints in a traditionally masonry chimney, or connections between pre-fabricated
metal chimneys and flue pipes. Minor leakage detected during this test, would therefore not be a
major risk when the installation is used during normal operating conditions, providing the point of
leakage does not indicate a fault that could get worse. However, if significant or heavy smoke leakage
is seen, the cause must be investigated and rectified. Broken components, incorrect fitting and
incomplete jointing of flue liners are the most common problems which cause major leakage and
require remedial action.
1 If there is an appliance fitted at the base of the bottom of the chimney, burn some newspaper in
the fire/grate for 2 to 3 minutes to establish a flue draw. A longer warming up time may be
needed with wet or cold flues. If there is no grate or fire box fitted use a blow lamp for 10 minutes
or more to establish a flue draw. It should be realised that neither of these methods create the
same temperatures or volume of hot gases that would normally be created whilst the appliance is
in use. They therefore are intended to assist the testing and not simulate real conditions.
2. Place two flue testing smoke pellets on a brick or similar in the opening at the base of the flue or
in the appliance if it is fitted. Follow the pellet manufacturers safety instructions.
3. Ignite the pellet and when it starts smoking seal the opening with a board or plate sealed at the
edges or if an appliance is fitted, close all doors, ashpit cover and vents.
4. When smoke begins rising out of the top of the chimney, seal the top of the flue, terminal or pot.
(i.e. use an inflated football bladder or plastic bag sealed in position with tape).
5. Examine the full length of the chimney for any leakage of smoke. If possible check for signs of
smoke leakage from wall cavities at the sides and back of the chimney, if it is built into a wall.
Also check for smoke leakage at openings around windows near to the chimney and the roof
space area.
6. If any smoke is seen establish the point of leakage and carry out remedial work to correct any
faults.
7. After completing the remedial work repeat the testing procedure until no major leakage or fault is
apparent. Remove the closures at the top and bottom of the chimney.
