The general best practice is to use the thickest possible air filter for maximum efficiency. But never try to force an air cleaner to fit in a space it's not designed for. If you attempt 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. Most HVAC professionals will tell you that thicker filters work better than the common 1-inch oven filters.
Thicker filters, known as multimedia filters, are usually 4 to 5 inches thick compared to the ubiquitous 1-inch filters that can even be purchased at grocery stores. In short, the thicker the filter, the more dirt it can hold. This means you can enjoy a longer period of time before needing to replace the filter. The oven filter change time will be much longer.
Another important difference between 1-inch and 2-inch filters is their efficiency. Why can we conclude that thicker filters are more efficient? For some of the following reasons. However, there are some cases where 1-inch and 2-inch filters can be on par when it comes to efficiency. All of this depends on the MERV rating of the filter.
The MERV rating is the classification that measures how well the filter blocks particles. Your oven processes the air that surrounds your home at a rate of seven times an hour in an average home. Poor airflow can mean that some of the rooms in your house will not heat up properly. With more airflow, your home environment will be more comfortable and it'll heat your target temperature more easily.
If improving air quality is a priority for you, filter depth doesn't matter as much as the MERV. But why is there such a big difference in their life expectancy? It's because thicker air filters have more square feet. If you need a high humidity filter for air purity due to respiratory problems, buy an external air purifier. Poorly installed one-inch filters whereby air circulates around the frame (even causing the frame to bend and deform) are very common.
Remember that having the best filter for your unit will provide the best air quality for you and your loved ones. You might be thinking that this type of air filter isn't something you'd prefer the air you breathe to flow through. The more and smaller particles a filter traps, the faster it will fill up with dust, pollen, pet hair and dander, etc. Of course, this could be very effective in stopping dirt, but it also serves to stop air flow to the unit.
You can also use air ionizers, which can help treat the air around your home by eliminating allergens and viruses.