The filter frames used in 20x20x1 air filters are typically made of beverage cardboard, which is strong and durable. Flat panel filters are constructed on a flat cardboard frame and are filled with fibrous materials such as polyester, fiberglass or other types of efficient synthetic materials. These filters are inexpensive, but they are also less efficient compared to pleated filters. The main purpose of these filters is to trap debris and larger dirt particles.
When used in the real world, the air in your home is constantly recirculated through the ducts and passes through the filters each time, resulting in an increased cumulative effect. When deciding what type of air filter is right for your air conditioning system, it is important to consider the filter's retention efficiency. MERV 7 general purpose pleated air filters offer 35% to 50% efficiency for filtering particles between 3 and 10 microns in size (such as mold spores, dust removal aids and cement dust). If your HVAC system uses a thicker filter (typically 4 to 5 inches and usually mounted on the air handler), it's likely to be specifically designed for medium-efficiency MERV filtration.
The MERV ratings reflect the performance of the filter in all its components. It is important to note that most home air conditioning systems don't include any fan or motor powerful enough to expel air, so using a HEPA filter can damage the entire system. These filters are often installed in the air conditioning systems of food and beverage, healthcare, hospitality, education and industrial facilities to remove contaminants from the air stream and improve air quality. The Environmental Protection Agency (EPA) generally considers air filters in the range of 7 to 13 to be equivalent to HEPA filters.
They are installed in wall-mounted return air vents (most common in the south) or in the air filter (more common in the Mid-Atlantic and Northern states, where the air handler is usually placed in the basement, near the oven). During a wildfire, you'll need to change your filters more often than you would under normal air conditions, and there are some indicators that can help you know when it's time to replace one. Pleated air filters capture airborne contaminants more effectively than non-pleated air filters, as the pleated filter medium provides more surface area for trapping contaminants than non-pleated filters.
