Do HEPA Filters Help With Asthma Symptoms?

by Eli Hendel, M.D. Medical Reviewer

Indoor air pollution continues to be one of the main triggers of respiratory illness, particularly asthma. One of the ways to reduce this burden is through the use of High Efficiency Particulate Air (HEPA) filtering machines.

To examine how effective HEPA machines are, a study was conducted by the Intermountain Healthcare Medical Center. The results were presented at the September 2018 European Respiratory Society’s International Congress in Paris. The two year small study offered data after researchers monitored air quality for 12 weeks in the homes of patients who had respiratory problems and compared it to outdoor air quality.

The researchers found that HEPA filters reduced fine particulate matter by 55 percent. Fine particulate matter is defined as particles floating in the air that measure 2.5 microns which means they are small enough to be inhaled and reach the small airways. The term often used is “respirable” particles. This measure is known as the PM2.5 count which refers to the small airborne particles in areas with heavy air pollution. When inhaled in significant amounts, they can lead to respiratory problems, heart attacks or worsen symptoms in someone who has respiratory challenges.

This study is significant because this is the first time that the findings regarding the impact of HEPA filtering were actually measured in the setting of the home environment of individuals already diagnosed with respiratory disease.

The take home message is that while there may not be much that can be done on a personal level to control outdoor pollution, with this simple device you can modify the effect of the outdoor air that gets inside. The accessibility of these devices will be an important determinant of acute exacerbations in patients with asthma and COPD.

Air purifiers have increased in popularity. They can be either small stand-alone devices or in the case of more sophisticated offerings, incorporated into heat, vacuum and air conditioning (HVAC) units in larger homes and other large dwellings and work spaces. The advantage of these larger systems is that it can remove particles or larger amount of air pollutants in a shorter period of time. The disadvantages is little control of how the units will personally benefit you and your family.

The stand-alone air purifiers offer two types of services:

Active air purifiers use ionization to clean the air. The system uses charged electrical surfaces to generate electrically charged particles known as ions. These ions are then attracted to and trap the pollutants in a charged collector plate. One of the drawbacks of this technology is that it produces ozone or other oxidant gases as byproducts. Ozone is a molecule that contains an extra oxygen molecule, and it can be toxic at certain levels to humans. Most manufacturers claim that the concentration of ozone is less than 0.5 parts per million (PPM) which is considered a safe standard. I’m not a fan of these units.

Passive air purification uses air filters to remove the polluting air particles. With the High Efficiency Particulate Air (HEPA) filter, the goal is to remove particles as small as 2.5 microns thereby lowering the indoor PM2.5 count. You can also make sure to air seal your home. This can help to limit particulate intrusion.

HEPA filters do not generate ozone or other products.

The U.S. Department of Energy has standards that apply to manufacturers to meet HEPA filtration standards and requirements. It includes the standard that the device must be efficient in removing 99 percent of airborne pollutants 0.3 microns or larger in size. When purchasing a HEPA unit be aware that it can advertise disclosures - “HEPA-like” or “HEPA-type” which the consumer should recognize as implying that they do not meet true HEPA standards.

There is constant innovation in the industry with some HEPA units now using technology including

  • Ultraviolet germicidal irradiation to kill bacteria and viruses

  • Titanium dioxide to neutralize acidic gasses

  • Photocatalytic oxidation, a newer technique that can oxidize and degrade organic contaminants.

The most important considerations are the ability to remove volatile organic compounds (VOCs) which are products of metabolism of molds that can cause serious health hazards beyond just the inhalation of mold particles.

The best known names in commercially available air purifiers those made by Levoit Technologies, Bionaire, Guardian industries, Hamilton Beach, and Houselog. The prices are reasonable for an initial investment but do require upkeep with frequent changes of filters.

Additional considerations:

  1. Make sure the label reads “true HEPA” to be sure that it meets US Department of Energy standards which means removal of 99 percent of particles 3 microns and above.

  2. Look to see if it says “ozone free” if it uses ionizing radiation. If it does not it may say that the ozone concentration is like outside levels. This is not safe nor acceptable.

  3. Some of these units have aromatherapy built in to remove odors, especially it targets homes with pets. Some asthmatics are sensitive to the oils used in aromatherapy.

  4. It would be useful if you can see the unit in operation so you can hear the noise it makes. Test the different speed settings to make sure it won’t interfere with sleep at night.

  5. Look into the air inlet. You want the unit to process most of the air in the room. Some units have a 360-degree inlet to absorb air from all room angles

  6. Inquire whether it has ultraviolet light or titanium dioxide technology. Those units will have the additional benefit of removing VOCs and mold spores.

  7. Some of these units disclose the clean air delivery rate (CADR) which is the standard of effectiveness of HVAC (central heating, ventilation and air condition units) determined by cubic Feet per minute. This may be important when considering room size where this unit will be stationed. A good number Is 100 CFM

  8. Some units advertise power used and room or area size it can clean. Since these units run 24/7 consider getting a letter from your doctor to submit to the local electric company so that you can possibly negotiate better rates.

A HEPA device or system can be an easy and affordable way to limit triggers if you have respiratory disease and it can dramatically help young children with asthma or other respiratory challenges.

You can't control weather, winds, vegetation, large fires or other air quality issues that occur outside. Staying indoors is recommended when the air quality is unhealthy. Having an indoor air purifier can be an effective preventive measure.

Eli Hendel, M.D.
Meet Our Writer
Eli Hendel, M.D.

Eli Hendel, M.D., is a board-certified internist/pulmonary specialist with board certification in Sleep Medicine. An Assistant Clinical Professor of Medicine at Keck-University of Southern California School of Medicine, and Qualified Medical Examiner for the State of California Department of Industrial Relations, his areas include asthma, COPD, sleep disorders, obstructive sleep apnea, and occupational lung diseases. Favorite hobby? Playing jazz music.