When it comes to air quality in residential homes, filters with a MERV rating of 17 to 20 are rarely necessary. A MERV rating of 13 to 16 is considered hospital-level air quality, so it's unlikely that your home would need anything higher. However, if you do decide to use higher MERV filters in the future, it's important to make sure that the rest of the system is configured to handle the biggest restriction that filters create. In general, filters with higher MERV ratings capture higher percentages of particulates as well as smaller particles.
MERV-13 is practically the highest you want to go in a household. If your home's HVAC system isn't capable of handling MERV 13, opt for a filter with the next highest possible rating. It's important to note that sometimes, due to the unintended consequences of high MERV filters, the cure can be worse than the problem. When you have a filter of MERV 13 and above, it is more similar to the material you would find in an N95 dust mask.
Surgeries and HVAC systems use MERV filters, but they do not use fiberglass. Mcmaster Carr manufactures the Merv-15 airbags that some universities are testing for face masks. This MERV filter is questionable, as it will actually be effective for this use since it needs an electrostatic charge that it does not receive when placed in a mask. Not all filters have a MERV rating, and many of them are purchased at big box stores. High MERV filters offer superior filtration, trapping everything from construction dust and tobacco smoke to bacteria.
However, as the MERV rating increases, the filter becomes more restrictive and more pressure and energy will be needed to push air through it. Home Energy published an article by Dave Springer of Davis Energy Group at the time, about the pressure drop and energy use of various MERV filters.
