Air ducts are responsible for pushing air into each of your rooms. Over time, dust particles, dirt and even harmful microorganisms start to build up on their surfaces. When your AC is running, it pushes this dirt and dust around, blowing it back into your rooms. If you can see dust or mould, then that is a key indicator that it is time to schedule an AC duct cleaning service. However, the ducts in your home are mostly behind walls and it is unlikely that you will be able to directly tell if a clean is required. If your ducts have not been cleaned for over a year then you can safely assume that dust and dirt will be starting to settle. If you are noticing an increase in the suffering of allergies from family members this may also indicate that your ducts need cleaning. If you are moving into a new apartment or villa one of the first things you should do is to schedule a full AC service and duct clean. You don’t want any residual dirt from the previous owners to be locked in your AC system. Scheduling an immediate clean also means you start with perfectly clean ducts and this will help you to keep track of your timings for future AC duct cleaning and servicing.