If you have allergies or asthma, indoor air pollution can trigger your symptoms. Most people don’t realize that indoor air pollution levels are actually much higher than those outdoors — two to five times higher, says Julie McNairn, MD, an allergist and immunologist in private practice in Middletown, Ohio.
“The sources of the pollution can be any number of things, one of which is allergens,” such as dust mites, mold, and pollen, explains Dr. McNairn.
Common Indoor Allergens
Common indoor allergens include:
When these particles become airborne, you can breathe them in and experience an allergic reaction.
The heating, ventilation, and air conditioning (HVAC) system in your home can both harbor and spread mold and other allergens.
Optimize Your HVAC System
Filters can help minimize exposure to allergens from your HVAC system, notes McNairn. Filters can be built into the air ducts in your home, but keep in mind, not all filters are created equally.
The effectiveness of filters is “measured in something called MERVs [minimum efficiency recording value],” says McNairn. MERVs range from 1 to 20, with 20 providing the highest level of particle filtration.
Types of HVAC Filters
Other things to know about HVAC filters include the following:
- Flat panel filters. These filters, put in place by most furnace manufacturers, generally have a rating of one to four MERVs, and are designed to protect the furnace, not improve indoor air quality.
- Medium efficiency filters. These pleated furnace filters have a higher surface area and, therefore, filter more particles out of the air. Their MERV rating ranges from five to 13.
- High efficiency filters. These filters have MERV ratings of 14 to 16, and remove even smaller particles than pleated filters.
- HEPA filters. High-efficiency particulate air (HEPA) filters have MERV ratings of 17 to 20, and are not typically recommended for centralized home HVAC systems unless major — read expensive — updates are made to the system. This is because high energy and HEPA filters can be so efficient that your HVAC system ends up requiring more energy to power the fan that gets air circulating.
Since higher efficiency and HEPA filters tend to put so much stress on your HVAC system, McNairn recommends medium efficiency filters for most people. “They are reasonably effective at removing small to large particles,” she says.
Controlling Indoor Allergens: Regular HVAC Maintenance
It is important to change filters regularly — as recommended, or every two months during use — and follow any maintenance instructions recommended by the air conditioner system’s manufacturer. If you suspect mold may be growing inside your air conditioning system, you may want to consider having the air ducts cleaned.
If you see mold particles growing near the ducts or on other components of the system or if you smell a musty or moldy odor coming from your vents, consult a duct cleaning professional to check for an accumulation of mold.
Another thing you may want to consider when building a new home or replacing your existing HVAC system is a unit that replaces indoor air with filtered outdoor air.
“Some HVAC systems actually draw in air from the outside to the inside to help with the ventilation,” explains McNairn. Increased ventilation in your home can help reduce mold growth and other sources of indoor pollution