A smoke integrity test, or smoke test, is necessary if you are installing a new appliance, are re-opening an old fireplace or an old chimney. These tests try and identify any cracks and leaks in the chimney as these could cause dangerous gases to escape. It is recommended that surveys are taken of chimneys on a regular basis. This might identify any problems before they can become dangerous, in the case of a crack or blockage. These can lead to carbon monoxide poisoning which can be fatal.
A smoke integrity test involves setting off a smoke pellet in the fireplace of a chimney. As this burns the smoke should only expel from the correct place, usually one chimney stack. If smoke is found present elsewhere then there might be a blockage or crack in the flue (the vertical shaft leading up to the chimney stack.) Although it is possible to undertake a smoke test by yourself, it is highly recommended that a qualified chimney sweep does this for you as it can be dangerous and difficult to identify problems without adequate training.
Surveys are also important. These should be undertaken regularly to make sure that the chimney is safe. CCTV (Closed Circuit Television) is often used to take a survey of the flue and the chimney stack. This recording is then viewed by a trained chimney sweep who will then be able to identify any problems. It will normally be possible to arrange for a survey to be completed on the same day as the chimney sweeping.