HVAC servicing should include not only regular filter changes at the correct intervals, but also a deep clean of all of the internal surfaces of the ventilation system downstream (clean air side) of your filter bank.
Technicians perform a chemical clean of the entire ventilation system, from outside air intake right through to supply air ceiling grilles. Repainting flaky paint, repairing rust damage and replacing leaking or damaged seals can all be done at this step. Any damaged or aging filter holding banks are repaired. The air supply fan should also receive a full clean. This increases air movement efficiency; a dirty fan is less efficient as it requires more power to run and can cause vibration issues. HVAC components to be cleaned and sanitised include: