Purchasing a new filter is not an impulse decision. It is crucial to do some research beforehand to make sure that your filter will work best to suit your needs. One of the leading indicators of filter efficiency is the MERV rating. What is MERV rating? MERV stands for Minimum Efficiency Reporting Value. Designed in 1987 by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the MERV rating gives an accurate description of air filter efficiency.
You may be asking yourself, “How do I know which MERV rating is best for me?” There are a number of different ways to determine which filter type is most suitable, and in the case of MERV ratings, a higher rating doesn’t necessarily indicate a better filter. The ratings given to a filter describe the worst-case performance of a filter when encountering particles of a specific size. The scale ranges from 0.3 to 10 micrometers. Higher-rated filters correlate to a higher percentage of particles being captured. Below is a breakdown of the MERV rating scale.
Particle Size: >10 μm
Filters with this rating are typically found in residential window AC units. These filters offer minimal filtration, blocking particles that include pollen, dust mites, textile fibers, and carpet fibers. While these filters will obstruct basic particles, filters with a MERV rating of 1-4 will not do an efficient job of removing all airborne contaminants.
Particle Size: 10.0-3.0 μm
These filters can be found in standard residential areas, commercial buildings, and many industrial workplaces. Filters with a MERV rating of 5-8 can block particles of a smaller size such as pollen, pet dander, dust mites, lint, and mold spores. These filters are recommended for everyday home filtration.
Particle Size: 3.0-1.0 μm
Filtering particles such as humidifier dust, lead dust, smog, odor, and legionella, MERV 9-12 filters allow for more controlled environments. These filters are typically found in superior residential buildings, better commercial buildings, and hospital laboratories. Filters with a MERV 9-12 rating are ideal for people with allergies.
Particle Size: 1.0-0.3 μm
Filters in this MERV rating range will not be typically found in residential buildings. These filters are used for more controlled air environments such as hospitals and surgery operating rooms. MERV rating 13-16 filters can block particles such as bacteria, droplet nuclei found in sneezes, smoke, insecticide, and most paint pigments. This level of filtration is recommended for the homes of people with respiratory issues such as asthma.
Particle Size: <0.3 μm
These filters block and absorb the smallest range of particles, and are used for the most controlled environments. As such, pharmaceutical and electronics companies utilize these high rated filters for their manufacturing cleanrooms, where it is crucial to have a sterile environment. Particles including viruses, carbon dust, sea salt, and smoke are all contained by filters in this category.
The Environmental Protection Agency of the United States recommends medium efficiency filters for residential buildings. Filters between the ranges of 5-13 do a reasonably efficient job of removing airborne particles. Filters with a higher rating run the risk of increasing airflow resistance which can cause your home system to run inefficiently. The highest recommended range for residential systems is 9-12; higher ratings are said to be suited for hospitals or commercial buildings where more a sterile environment is required.