How to keep your air ducts clean without paying for a cleaning

Updated November 10, 2026 · KeystoneProGuide editorial team

How do you keep air ducts clean?

Keep dirt and water out of them. The U.S. Environmental Protection Agency (EPA) says that preventing water and dirt from entering the system is the most effective way to prevent contamination, whether or not you ever have the ducts cleaned.

Its guidance, combined with ENERGY STAR's maintenance checklist, comes down to a routine anyone can keep. None of it involves a duct cleaning company.

Which filter should you use?

The filter stands between household dust and the inside of your system. The EPA's instructions are these:

• use the highest efficiency air filter recommended by the manufacturer of your heating and cooling system;
• change filters regularly, and more often if they become clogged;
• make sure no filter is missing;
• make sure air cannot bypass the filter through gaps around the filter holder.

Efficiency is measured by the MERV rating, which the EPA says reports a filter's ability to capture particles between 0.3 and 10 microns. The higher the number, the better the filter traps particles. If you decide to upgrade, the EPA's advice is to choose at least MERV 13, or as high a rating as your system's fan and filter slot can accommodate. It adds that you may need a heating and cooling technician to tell you the highest efficiency filter your system can take.

The two pieces of advice fit together. Go as high as the equipment allows, and no higher.

How often should you change it?

ENERGY STAR says to inspect, clean or change the filter once a month in a central air conditioner, furnace or heat pump. It warns that a dirty filter raises energy costs and can damage equipment, leading to early failure.

HomeAdvisor's cost guide suggests a change every three to four months. The EPA's rule is to follow the manufacturer's recommendations and to replace sooner when a filter clogs. A monthly look costs nothing and tells you which applies in your house.

How do you keep water out?

Moisture is the bigger risk. The EPA says moisture should not be present in ducts and that controlling it is the most effective way to prevent biological growth, which means mold.

• Watch the cooling coil. The EPA says condensation on or near the cooling coils of air conditioners is a major factor in moisture contamination. The condensate pan under the coil must drain properly. Substantial standing water or debris there needs immediate attention.
• Keep the drain clear. The EPA's mold guide says to keep air conditioning drip pans clean and the drain lines unobstructed. ENERGY STAR notes that a plugged condensate drain can cause water damage and affect indoor humidity.
• Check nearby insulation. The EPA says to look for wet spots on any insulation near the cooling coil.
• Fix leaks promptly. The EPA says to repair leaks and water damage promptly and properly. Its mold guide says wet materials dried within 24 to 48 hours will in most cases not grow mold.
• Seal and insulate ducts in unconditioned spaces. The EPA says ducts in attics and crawl spaces should be properly sealed and insulated so that condensation does not form.
• Mind the humidifier. If your system has in-duct humidification, the EPA says to operate and maintain it strictly as the manufacturer recommends.
• Keep indoor humidity down. The EPA's mold guide suggests below 60 percent relative humidity, ideally 30 to 50 percent, and says a humidity meter costs about $10 to $50.

What should a yearly service visit include?

Ask whoever services your system to clean the cooling coils and drain pans while they are there. That is the EPA's advice. It counts regular cleaning of those parts, along with filter changes and a yearly inspection of the heating equipment, as the normal upkeep of a heating and cooling system.

ENERGY STAR recommends a contractor's pre-season check-up each year. Its list for the visit includes cleaning the evaporator and condenser coils, cleaning and adjusting the blower and inspecting the condensate drain. How often air ducts should be cleaned sets out the yearly schedule in full.

What can you do in the rest of the house?

• Vacuum and dust regularly. The EPA suggests a HEPA vacuum, or the highest efficiency filter bags your vacuum can take. It notes that vacuuming raises dust into the air while you do it.
• Clean the registers. Return registers get dusty in normal use. They can be vacuumed, or removed and cleaned.
• Deal with sources. The EPA says the most effective ways to improve indoor air are to reduce or remove the sources of pollutants and to ventilate with clean outdoor air. Filtration is a supplement to those, not a substitute.

What should you do during building work?

Seal the supply and return registers and leave the system off until the dust has been cleaned up. That is the EPA's instruction for any construction or renovation work that produces dust.

What if you are replacing equipment?

The EPA has two points for anyone replacing an air conditioning system. Make sure the unit is the proper size for the house: one that is too big cycles on and off frequently and removes moisture poorly. And make sure all ducts are sealed at the joints.

On the second point, ENERGY STAR says about 20 to 30 percent of the air moving through a typical home's ducts is lost to leaks, holes and poorly connected ducts, with higher bills and less comfort as the result.

Does this routine mean ducts never need cleaning?

No. A leak, a flood, an infestation or a long period without a filter can still leave a system in one of the conditions the EPA says justify cleaning: substantial visible mold, vermin, or ducts clogged with debris. What the routine does is remove the ordinary causes.

The EPA is plain about the ordinary case. A light amount of household dust in ducts is normal, and it does not recommend that ducts be cleaned routinely.

For the tasks a homeowner should leave alone, see can you clean your own air ducts. For the energy side, see cleaning versus duct sealing. If you have reason to think the routine came too late, businesses that clean ducts are listed on the air duct cleaning directory page.

Sources

1. Should You Have the Air Ducts in Your Home Cleaned?, U.S. Environmental Protection Agency
2. What is a MERV rating?, U.S. Environmental Protection Agency
3. Air Cleaners and Air Filters in the Home, U.S. Environmental Protection Agency
4. A Brief Guide to Mold, Moisture and Your Home, U.S. Environmental Protection Agency
5. Maintenance Checklist, ENERGY STAR (U.S. Environmental Protection Agency)
6. Duct Sealing, ENERGY STAR (U.S. Environmental Protection Agency)
7. How Much Does Air Duct Cleaning Cost in 2026?, HomeAdvisor