Your home air filter is in place for a reason. Yes, it can filter out particulate that could otherwise make you sick or have an effect on your allergies or asthma symptoms. However, that’s more a feature of modern air filters. Filters have been engineered for furnaces and air conditioners since the beginning of the 20th century, since without them, the system could be pummeled by debris as the blower fan sucks in air.
An air filter is there to protect your health and your investment. But when it gets too dirty, it’s not really helping you at all. This isn’t just due to health concerns. (In fact, the lack of air circulation may help to stop even more particles from circulating!) Rather, it’s because a dirty filter raises the cost of heating and cooling.