I have a daughter with allergies. Having not experienced allergies myself, I have had to teach myself what I need to do around the house to help increase her quality of life -- especially in the fall and spring. One of the things I now put on my calendar is frequently checking and changing the filters. I choose to change the filters every three months. I know others who do it much more often. In my research, I came across the following facts.
Furnace filters were originally designed to protect the mechanical components of HVAC equipment from dust and dirt. As cases of asthma and allergies have increased, so did concerns about air quality. Some filters have now been designed to capture smaller and smaller particles of dust.
Microscopic particles can be small enough to defeat our respiratory defense systems, causing illness or aggravating respiratory conditions. Disposable, refillable and reusable filter choices exist to assist in cleaning the air in our homes.
To get the most usefulness out of the filters, it is important to change them regularly, usually at least once every season, and to use a filter that fits with the manufacturer's specifications. Filters capable of catching smaller and smaller particles - defined by a MERV rating -- can reduce the air flow to the furnace. A higher MERV rating means the filter can stop smaller particles. Efficiency of the furnace and filters will decrease over the life of the filter as small holes get plugged with dust and debris. It is also important to remember that filters only work when the HVAC fan is on. No air is filtered when the fan isn't running.