The short answer most contractors will give you: every 3 to 7 years. That's the National Air Duct Cleaners Association (NADCA) recommendation, and it's a useful starting point. But the real answer depends on your specific home the people in it, the pets, the age of the system, and the climate. After 11 years of cleaning ducts in St. Louis homes, here's what we actually tell our customers.
The Official Recommendation
NADCA recommends professional air duct cleaning every 3 to 7 years for most homes. This is the industry standard, based on how long it takes typical residential dust loads to build up to levels that affect indoor air quality and HVAC performance. For a healthy adult living alone in a newer home with no pets, 5-7 years is usually fine. For most family homes, the answer is closer to every 3-5 years.
Factors That Mean You Should Clean Sooner
Push toward the 3-year end of the range or sooner if any of these apply to your home:
- Pets that shed. Dogs and cats add huge amounts of dander and hair to the duct system. Two shedding pets can effectively cut cleaning intervals in half.
- Allergies, asthma, or respiratory conditions. Anyone in the household with sensitivity to dust, pollen, mold, or pet dander benefits from more frequent cleaning.
- Recent renovations. Drywall dust, sawdust, and construction debris settle deep into duct systems and stay there until extracted. After any major renovation, schedule a cleaning.
- You moved into a previously occupied home. You don't know when (or if) the previous owners ever cleaned the ducts. Better to start fresh.
- Smokers in the home. Tobacco residue coats duct interiors and continues to off-gas long after you can't smell it.
- Visible mold or musty smells. If the system smells musty when it kicks on, that's biofilm growing inside. Clean and sanitize.
- Water damage history. Any flood, leak, or water event near the HVAC system creates conditions for mold growth.
- Older home (50+ years). Older ducts have had more time to accumulate buildup and often have less efficient sealing.
Factors That Mean You Can Wait
Push toward the 7-year end of the range if your home checks all these boxes:
- No pets, or very low-shedding pets
- No smokers
- No allergy or asthma sufferers
- Newer home (under 15 years old) with no water damage history
- HVAC system has been regularly maintained with quality filters
- No recent renovations
- No musty odors or visible buildup at the registers
If you're in this category, every 5-7 years is usually plenty.
Why St. Louis Climate Matters
St. Louis's humid summers and pollen-heavy springs put extra stress on duct systems. Mold and biofilm grow faster in humid air. Spring tree pollen oak, maple, sycamore gets pulled into return registers in massive quantities. Compared to drier climates, most St. Louis homes need cleaning a year or two sooner than the standard recommendation.
Signs You're Overdue Right Now
Don't wait for a calendar reminder. Schedule a cleaning if you notice any of these:
- Visible dust collecting around register vents shortly after dusting the home
- Allergy symptoms that get worse when the HVAC runs
- Musty or stale smell when the system kicks on
- Higher energy bills than the same period last year
- HVAC running longer than it used to to reach setpoint
- Visible debris or webs at the register grilles
What About Dryer Vents?
Dryer vents are different. We recommend annual cleaning for any household every 6 months for families that do laundry every day or have long vent runs. Dryer vent buildup is a fire hazard, and lint accumulates fast. Read more about dryer vent safety.
Bottom Line
For most St. Louis families with kids, pets, or allergies plan on professional duct cleaning every 3-5 years. For lower-impact households, every 5-7 years is fine. If you're not sure where your home stands, give us a call. We'll ask a few honest questions and tell you whether you're due now or could safely wait another year. We'd rather earn a customer for life than push a job that isn't ready.