Any air filter rated higher than 13 will restrict airflow to the point of causing damage to your HVAC system, resulting in an additional expense to repair it. In general, filters with higher merv ratings capture higher percentages of particulates as well as smaller particles. And MERV-13* is practically where you want to be. Another unwanted effect of this reduced airflow is on the cooling side.
The air conditioner has a hot coil on the outside, the condenser and a cold coil on the indoor air handler. This cold coil has a specific preferred operating temperature. That temperature is based on a certain amount of hot air flowing through that coil and the coolant circulating through that coil's copper tube. With a higher merv filter that reduces airflow through this crucial part of the air conditioning system, the cold coil can eventually freeze and become an ice ball, restricting airflow completely.
Without giving further details, this causes more costly problems in the outdoor condenser coil. A merv rating of 13 to 16 is considered hospital-level air quality, so your home is unlikely to need more than that. According to the United States Environmental Protection Agency, filters in the 7-13 range often have little difference from higher merv ratings, but they will allow your system to work much more efficiently. Not all filters have a Merv.
Not all filters have a Merv rating %26, many of them are purchased at big box stores. While ASHRAE recommends merv 13 and 14, it's best to select a filter with the highest possible MERV rating for your specific HVAC system. When you have a filter from Merv 13 and above, it is more similar to the material you would find in an n95 dust mask. While air filters with a one-to-four MERV are effective at removing large particles such as carpet fibers, airborne paint droplets and sanding dust, they cannot help with contaminants such as hairspray, mold spores or even flour that might have escaped from the mixer.
As for the need for high-MERV filtering, it's easy to ignore it until you meet someone with allergies or asthma. MERV filters 9 to 12 are the best filters that a residential HVAC system can accommodate without major system modifications. It seems that it would be enough to just use the high merv filter media, blast it with compressed air, and then insert the filter into a pocket of the DIY face mask, between the two layers of fabric. Technology for HVAC units has progressed since then and most modern units in recent years should be capable of at least one MERV 8 filter.
However, high MERV filters offer superior filtration, trapping everything from construction dust and tobacco smoke to bacteria. According to Avery, in a new construction it is easy to accommodate a high MERV filter without static pressure penalty (see my previous comment). Increasing a filter to increase a filter to a higher MERV can increase the delta P through the filter. Although the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) suggests MERV 13, it may not be the most efficient option for some residential HVAC systems.
If your furnace's MERV rating is too high, it can force it to work too hard and leave it vulnerable to damage.