Ducting cleaning - does it make sense for Seattle area homes?

In the vast majority of cases, duct cleaning doesn’t improve the air quality.  It makes sense if you think about why dust has accumulated in the ducts.  The dust settled in the ducts because it was too heavy to remain in the airstream.  Therefore, duct cleaning is only removing dust that is permanently in the ducts.  It may look unsightly, but it’s not doing any harm and it won’t re-enter your home.

Researchers who have studied the issue discovered that a wind velocity of 160mph was required to re-aerosolize the dust back into the air stream.  This is the speed of a leaf blower.  Even the most high powered furnace only moves air at a fraction of this speed.

The ineffectiveness of duct cleaning an be easily proven with a particulate counter.  You simply collect a reading before cleaning the ducts and collect a second reading after the service is complete.  If the cleaning was effective, the numbers will decline.  In reality, the numbers don’t change.

Many companies are also pushing duct cleaning as a solution to health issues (even Covid).  These claims focus more on fear than sound science.  The air in your ducts is extremely dry, and therefore highly resistant to mold growth or other microbial growth.  In fact, in most climates, the air in your ducts is the driest air in your entire home.  If microbial growth were to occur in the ducts, it would have first grown on other surfaces in your home.

The claims regarding improvements in lowering viral loads are equally suspicious.  If anything, dirt ducts would be more likely to trap a virus, because they would increase the odds of a virus impacting the dusty layer inside the ducts.  Moreover, viruses cannot live (or replicate) outside of the human body.  Even the dirtiest of ducts is incapable of increasing the viral load in your home.

After inspecting thousands of homes, the only times I’ve encountered genuine issues with ducts is when a direct water leak has occurred above the duct.  Rodent issues can cause problems too, but typically these require full replacement, not just cleaning.

Cleaning your ducts will also have no impact on viral loads within your home.  Lastly, your furnace filter is placed after your return ducts, so any particulates that are transported through the ducts are removed out by your furnace filter.  Because of this, the EPA doesn’t recommend it unless you have an unusual situation.  Here is a link to their info: Should You Have the Air Ducts in Your Home Cleaned? | US EPA

For most clients, the best choice is to save the money on duct cleaning and instead put it toward a high quality furnace air filter.  These work very well and effectively improve the air quality in your home.

Now, this doesn’t mean there are never occasions when duct cleaning makes sense.  Certainly the return grille below could use a cleaning.

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