When it comes to improving air quality, the higher the MERV rating of an air filter, the better it will be at stopping particles. This means that a 1-inch filter with a high MERV rating could perform just as well as a 2-inch filter with the same rating. However, if your system only fits a 1- or 2-inch filter, a high MERV rating could be detrimental. A 1-inch filter with less surface space will clog up quickly and need to be replaced more often than a coarser filter.
The combination of a thin air filter with a high MERV rate can also restrict airflow to the point that it hinders efficiency and causes excessive wear and tear. For air filters to work properly, they must be the exact size for the filter housing; otherwise, dirt, dust, etc., will be absorbed by the gaps. Even if you sealed the gaps with adhesive tape, it would only last a short while before it came off. Your air conditioning system will last longer and be more efficient if you 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's relatively easy to remove the old 1-inch filter and insert a 2-inch filter. Most return air cleaner grilles also accept a 2-inch filter instead of a 1-inch filter. Parts that are particularly vulnerable include the air controller or oven blower motor that works overtime to push and draw air through the dirty filter and the heat pump or air conditioning compressor responsible for circulating refrigerant between the outdoor and indoor units. In other words, how many and how small particles it filters out of the air you breathe.
The more and smaller particles a filter traps, the faster it fills with dust, pollen, pet hair and dander, etc. If you want to improve air quality through better air filtration but don't want to modify your equipment, then a 1-inch MERV 13 filter is your best bet. This means that we could use this filter IF the duct system were in good condition; if the duct system is in poor condition, this filter will increase resistance to airflow too much. A 1-inch oven filter with a MERV rating of 6 to 8 will last up to 3 months even with fairly heavy oven use. The 4-inch thick air filter has an advantage over the 1-inch in terms of longevity, airflow and maximum filtration potential.
Ovens come in various sizes and configurations, so there's no one-size-fits-all filter. If it fits your oven, then a 4-inch air cleaner is better than a 1-inch air cleaner when it comes to improving air quality. The thickness of the air cleaner ranges from 1 to 5 inches deep; some options are more common than others, and your oven can dictate the thickness you can use. Reducing the thickness by one inch shouldn't be an issue; for example, you should be able to use a 4-inch filter instead of a 5-inch one. Keep in mind that if you need very high levels of filters, these are not as good as two overlapping filters.