The higher the MERV rating, the better the filter will be at stopping particulates. This means that a 1 inch filter with a high MERV rating could work just as well as a 2 inch filter with the same rating. If your system only fits a 1- or 2-inch filter, a high MERV rating could be harmful. A 1-inch filter with less surface space will clog up fairly quickly and will need to be replaced much sooner than a coarser filter. The combination of a thin air filter with a high MERV rating can also restrict airflow to the point of impairing efficiency and causing excessive wear and tear.
The best solution is to upgrade to a 2-inch filter or even a 4-inch filter. Many cabinets allow for either a 1 inch or 2 inch filter, and it is relatively easy to remove the old 1 inch filter and insert a 2 inch filter. Most return air filter grilles also accept a 2 inch filter instead of a 1 inch filter. The thickness of the air filter depends mainly on the system configurations. The general best practice is to use the thickest possible air filter to achieve maximum efficiency.
Filters only work if air has to pass through them. The filter has air resistance and a gap does not, so if you leave a gap of 1, an excessive amount of air will flow through the hole, which will further worsen the situation. Most air filters are 1 inch thick, but some systems can accommodate filters 2 to 5 inches thick. In our tests, we found that the thicker the filter, the better it works and the longer the replacement intervals. This means it's better for you and your heating, ventilation and air conditioning (HVAC) system. For the same length and width, you can get 1 inch, 2 inch, 4 inch and even thicker filters.
And all of them will fit your oven. But are they all equally good for you? If you measure the filter slot and it is large enough to accommodate the coarser filter, then you can use it. If a certain amount of dirty air passes through both, the number of “unclogged” pores will be greater in a coarser filter than in a thinner one. Whatever you do, don't use two filters 1 as others have suggested, as they will further restrict airflow and could damage the system. Therefore, if you choose a filter 1 with a high MERV rating, you will have to change it every month or two when the oven, heat pump, or air conditioner is used heavily.
For more information on individual products that use filters, such as air purifiers, room air conditioners and dehumidifiers, please refer to their specific buying guides. This means that with a filter 1, the air flow will be restricted much faster as the filter becomes covered with dust. Get a cheap 1 inch and a 1 inch face and place the face a second after the cheap one in the airflow. Like length and width, thickness is an important part of sizing the furnace filter and getting the right fit to optimize performance. The thickness of the air filter ranges in size from 1 to 5 inches deep; some options are more common than others, and your oven may dictate the thickness you can use.1-inch pleated air filters have higher MERV ratings for one simple reason: they have more surface area to trap particulates.
If you try to use a 4-inch thick air filter for a system that is made for a 1-inch thick filter, the efficiency will actually be worse. At the same time, a coarser filter is less restrictive and will allow better flow of purified air.