When duct cleaning is genuinely worth doing
There are specific triggers. Remodeling with the system running, which puts drywall dust through the whole duct system. Visible debris in the ducts or blowing out of the registers. Rodent or insect intrusion, including nesting material in the plenum. Water intrusion from a roof leak or a flooded attic. Smoke damage after a fire.
What these share is that something identifiable got into the ducts. If you can name the event, cleaning is a reasonable response to it.
When we will tell you not to bother
There is no maintenance interval for duct cleaning. Ducts are not filters. In a house with a properly fitted filter and a sealed return, the inside of the supply ducts stays reasonably clean on its own, because the air reaching them was already filtered.
Be careful with the cheap whole house special. That price covers a shop vacuum at a couple of registers, and the visit usually ends with a much larger recommendation. Cleaning that skips the plenum, the coil face, and the blower wheel has skipped the parts that were dirty. Saying so plainly is part of how we ended up with 770+ Google reviews at a 5.0 average.
If the complaint is a smell, the ducts are usually not the problem
The most common reason people call for duct cleaning is a musty smell when the system kicks on. That smell almost always comes from the evaporator coil, not the duct walls. The coil is wet whenever the system runs, it sits in the dark, and the dust reaching it is organic. That is a growth surface, and cleaning the ducts leaves it untouched.
The durable fix for a coil that keeps doing this is a dipped coil, one with a factory applied coating that growth does not adhere to well. A UV lamp aimed at the coil is the other half of that conversation.
Fix these before you clean anything
A stopped condensate drain or a dried out trap is one of the most common and most preventable service calls we run, and it produces odors that no amount of duct cleaning addresses. We check the trap and the pan first.
Duct leaks are the other one. If your return leaks in an attic running past 130 degrees in July, you are pulling attic air, dust, and insulation fibers into a system you just paid to have cleaned. Sealing comes before cleaning.
What we look at before quoting duct cleaning
- The actual complaintWhether you are describing dust, a smell, or a specific event.
- Evaporator coilThe coil face and drain pan, the usual source of a musty smell.
- Condensate trapA stopped or dry trap producing odor or standing water in the pan.
- Return leakageOpenings pulling attic air into the system downstream of the filter.
- Duct interiorA direct look at the plenum and a sample of runs, not a guess.
- Flex liner conditionTorn liner, which is a replacement issue and not a cleaning issue.