While I am quite conscientious about taking care of the oil furnace & a/c, it never occurred to myself and others to worry about the HVAC duct.
I make a official habit of replacing air filters every month.
I call to schedule professional upkeep for the a/c in the Spring & again in the fall for the oil furnace. I am a bit annoyed that the Heating, Ventilation, & A/C professional never mentioned the need to inspect & service the duct system, however the network of pipes responsible for distributing heated & cooled air to every room in the apartment is concealed behind walls & ceilings. It is essential to both the oil furnace & a/c. If there are tiny holes or leaks at the seams, the conditioned air is allowed to escape. I pay for heated & cooled air that just disappears, because the air doesn’t reach the particular rooms, it makes it much more taxing for the oil furnace & a/c to achieve the desired temperature level. The equipment then is forced to run longer, work harder & use more energy. The rooms think cold or warm & there’s a greater risk of malfunction. There’s also the higher probability of air contamination. Those same leaks welcome in dirty, outside air. Every time the oil furnace or a/c starts up, it can spread dust, dander, bacteria, mold spores, fumes & all sorts of allergens into the breathing air, and when I had the HVAC duct inspected, I l acquired that 25% of our conditioned air was escaping by way of imperfections. The specialist also found a significant buildup of debris within the ducts that was restricting airflow.