These two services get bundled, separated, skipped, and confused constantly, and the confusion isn’t harmless, because the part most often skipped is the part most likely to ignite. Two minutes of clarity:
The sweep: cleaning the highway
Rods and brushes matched to the flue’s shape run its full length, clearing deposits from a basically uniform pipe. Efficient, effective, and what everyone pictures, the full process here. The flue’s geometry is exactly what brushes are designed for.
Chamber cleaning: clearing the on-ramp
The chamber’s widening funnel and corbelled ledges defeat straight brushes. Proper cleaning works from the firebox with shaped tools, clearing each shelf and the sloped walls individually, slower, more manual, and dealing with deposits that are typically thicker than anything in the flue.
Why the split matters to you
Unsure what your last cleaning actually covered? One look from below answers it, and you’ll see the photos either way.