Tools for Cleaner Indoor Air: A Few Things to Consider

Barb Allen illustrates the differences between using air cleaners and air purifiers to improve indoor air quality.

When people think about devices to improve indoor air quality, the term “air cleaner” is often used interchangeably with “air purifier.” However, there are important distinctions between these two devices.

Air cleaners, whether a portable unit or whole-house unit that is part of the HVAC (heating, ventilation, and air conditioning) system, use filters to remove dust and particles from air. When selecting a portable unit, it’s important to consider the size of the room or area. If a whole-house system already exists, choosing the correct filter is key. Although HEPA (high efficiency particulate air) filters are the most effective, if the HVAC system was not designed with HEPA filtration capabilities, using a HEPA filter can strain the fan/motor that is powering the air flow.

The most common HVAC filters consumers will encounter will be labeled with a MERV (minimum efficiency reporting values) rating, scaled from 1-16. This rating tells how effectively the filter traps small airborne particles such as dust, pollen, mold spores, pet dander, and tobacco smoke. Although higher MERV ratings are more efficient, the recommended MERV ratings for residential filters are between MERV 7 and MERV 13. Most residential airborne contaminants can be removed with an air filter within this range. (Filters higher than MERV 13 are usually found in hospital environments.) Choosing an HVAC filter that is the most effective at reducing these particles means selecting the highest-rated filter that system fan can accommodate. To filter gases, choose a unit with an activated carbon filter or other filter designed to remove gases.

Air purifiers use an electric charge to collect particles on a plate as they pass through the device. Purifiers tend to be better at getting rid of biological contaminants such as airborne pathogens that cause sickness, but are less effective at filtering and reducing larger particles like dust and pollen. Additionally, many air purifiers generate ozone which is a highly reactive molecule that is harsh on lung tissue. The U.S. EPA suggests avoiding any unit that produces ozone.

A key consideration is the effectiveness of a unit at removing particles of different sizes, which are sometimes represented with examples of smoke (smallest), dust (medium), and pollen (largest). The smallest particles (<PM2.5 or less than 2.5 microns) are invisible to the naked eye but carry some of the largest risks for respiratory issues, while the larger pollen particles are common causes for allergy issues.

Size comparisons for particulate matter (PM) in micrometers (μm). Note that PM2.5 is not visible to the naked eye. Fine beach sand 90 μm in diameter. Human hair 50–70 μm in diameter. PM10 ≤10 μm in diameter. PM2.5 ≤2.5 μm in diameter.

courtesy of Barb Allen

FOR MORE INFORMATION:

Visit https://www.epa.gov/sites/production/ files/2018-07/documents/guide_to_air_ cleaners_in_the_home_2nd_edition.pdf.

Barbara Allen is an Environmental Health Project Director and MSU Extension Associate Specialist.