When it comes to air filters, the MERV rating is an important factor to consider. MERV stands for Minimum Efficiency Report Value, and it is a measure of how effectively a filter can prevent dust and other contaminants from passing through it. The higher the MERV rating, the better the filter is at trapping small particles such as bacteria, tobacco smoke, and burning firewood. The MERV 10 filter is capable of removing 99.99% of 0.5 micron particles under real field conditions.
On the other hand, a MERV 15 filter can remove 99.999%. To put this into perspective, cloth bags found in most dust collectors can only remove 98.7% of 1.0 micron particles. The MERV 10 filter can filter 85% of 3.0-10.0 μm particles, while the MERV 12 filter can filter 90% of the same particles. When choosing an air purifier, it is important to select one with a filter that has the highest possible MERV rating. However, using an air filter with a higher MERV rating than recommended by the boiler or air conditioner manufacturer may affect its performance.
The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) uses particle size to classify MERV values. Filters with a MERV 13-16 value are the most restrictive and can trap the smallest particles, such as bacteria, tobacco smoke and burning firewood. These filters are slightly more restrictive than MERV 1-4 filters and have the ability to trap mold spores and some pet dander along with dust and pollen. In general, if you want the best air quality, you should buy a filter in the MERV 13-16 category. However, if you use a higher MERV rating that traps more particles, you may need to change the filter more frequently.