MERV stands for Minimum Efficiency Reporting Value, and every furnace filter has a MERV rating that has been established through a number of tests. The resulting rating determines how efficient the furnace filter is in capturing various sizes of particles that pass through it when it's turned on. The rating scale goes from 1 (least efficient) up to 16 (most efficient), but that doesn't necessarily imply that all homes absolutely need a furnace filter with the MERV rating of 16. Clean and healthy air can be provided by filters with a rating as low as 6.
How MERV Rating Are Established
There are two main tests that establish the MERV rating of a furnace filter: The Dust Spot Efficiency Test and The Arrestance Test. In the first test, the filter is measured through means of its ability to remove dust particles from the air, and the second test measures its ability to remove synthetic particles from the air. These two tests can thus demonstrate whether or not the filter can remove any type of particle from the air of a home. Filters with high ratings have been proven to be able to remove as much as 90% of particles detected in the air, both atmospheric dust and injected synthetics.
How To Choose a Filter Depending on Its MERV Rating
As previously mentioned, not all homes will need a furnace filter with a MERV rating of 16. These can be quite expensive, are generally designed for people suffering from severe allergies. It's important to keep in mind that a filter's price is directly proportional with its rating. Therefore, the cheapest will be the ones with a low rating, and the most expensive the ones with a high rating. Naturally, this makes sense, because low ratings mean poor quality, while high ratings mean superior quality, so you pay for what you get.
Usually, the needs of most families and households are covered by furnaces with 6, 8, 11 or 13 rating points. If you're unsure what level of furnace filter you need to buy for your home, an important step in deciding is closely analyzing your and your family's medical history. If anyone in your home suffers from allergies, it's best to buy a filter with a high rating, perhaps a 13 (with the condition of the allergies not being too severe). If you and everyone else you share your home with are perfectly healthy, then a 6 or an 8 will suffice. All in all, the most important thing to keep in mind is that you have to put your needs (and those of your loved ones) first.