If there do not appear to be any immediate problems then air ducts can be checked every few years. Without checking your air ducts you cannot know when they should be cleaned. It is important to know that even if your system appears to be working fine, it might actually be in need of a clean and could possibly be functioning below its capacity. In such a case, the only evidence you would have for an under optimized HVAC system would be a larger than usual energy bill.
Eventually every home will need to have their HVAC system (all the inner components of your cooling and heating system) cleaned. This is part of regularly scheduled home maintenance and is not usually associated with any urgency.
Home owners of a newly bought residence should have their air ducts cleaned and checked before moving in. Cleaning air ducts before moving in is just like cleaning the bathroom or carpets in that the end goal is to remove any trace of the previous tenants. Imagine if the people who lived in your newly purchased home were smokers or professional painters. Surely after a few days of smoking or painting the associated fumes begin to gather in the HVAC system where they are ventilated and circulated out. If the previous tenants did not clean their air ducts, then the air being circulated in your home is actually their old air. Second hand smoke is bad enough but do you really want second hand air?
Allergy sufferers and residents of post construction (i.e., home remodeling) also risk breathing in indoor air pollution. Construction releases tiny particles of saw and drywall dust that float about in the air. A portion of this dust will be sucked back into the HVAC system to be ventilated with other air. Since these particles are solid they cannot be filtered out so they are just pushed back into the air and into your lungs when you breathe. By the same token dust and dander allergens behave exactly like sawdust particles in that they just participate in the cycle system without actually being filtered out. Allergy sufferers who have their arid cuts cleaned as well as their carpets and upholstery are guaranteed to feel immediate relief and results.
Carpet Cleaning Alexandria is happy to announce that we had partner up with Dustless Duct a leading air duct cleaning company!