A well-planned, well-built ventilation system is just one factor, but a very important one indeed when it comes to ensuring good quality of indoor air. It must be cleaned as well. Ventilation ducts must be inspected and if necessary, cleaned, both before the building enters use, and every three years subsequently. Ducts should be cleaned for two reasons: from the standpoint of the health and well-being of the intake pipe and for fire safety reasons in the case of the exhaust pipes. If fire breaks out inside the building, the ventilation equipment and ducts can contribute to the spread of fire and smoke, accelerating the fire. Malfunctions in the ventilation equipment itself can also cause a fire. If a ventilation system is operating in a space where there is a danger of explosion, too much combustible compound or dust can accumulate in the ducts, which can lead to an explosion. The internal surface of the ducts nearly always accumulates dirt.
Dust that adheres readily to the duct is usually the result of many sorts of industrial processes, but in office buildings as well, an average of 1 g/m2 a year accumulates in ventilation ducts, about 80% of which is inorganic. Cleaning of ventilation systems has been obligatory in Estonia since 2004.
Ventilation ducts are cleaned using brush machines, which are built to allow the brushes to access hard-to-reach crevices as well as narrow spots in the ducts. Using a rotation direction changer, the brush rotates in the necessary direction in the duct’s recesses. Vent units are cleaned separately, using a special vacuum cleaner. If ducts have limited access, then cleaning hatches are installed on the site.
To clean the intake ducts, vacuum suction must be used, using equipment rated at 2500-8000 m3/h. They are equipped with pleated filters that also perform the function of trapping dirt. As it is not possible to direct the air that escapes the vacuum suction device, the device is equipped with a fine or microfilter. The vacuum device creates a current of air similar to a wind gust with a speed of 15-30 m/s, ensuring total removal of debris from the duct.