Equipment made for the job
Duct cleaning is done under negative pressure: a machine with HEPA filtration pulls air out of the duct while rotary brushes and compressed-air whips loosen the dirt. The dust leaves the building instead of settling on your sofa.
For units, we dismantle and wash coils, blower wheels and drain pans rather than spraying the front panel. Disinfection is applied by fogging or misting so it reaches the surfaces where mould and bacteria actually grow.