steel dustpan to help prevent distribution of soot and dirt

I was reading my furnace manual and I came across this. It says for my upflow furnace, a Carrier 30 y.o. oil burner (no boiler), model 58HV085:
"Upflow models are equipped with steel dustpan to hep prevent distribution of soot and dirt particles through the duct system. "
I though if soot was coming through the ducts, it mean there was a hole in the firewall. If the fire is on the other side of the firewall, how can soot be in the ducts? And what kind of dirt particles are they talking about?
Less important: What would the "dustpan" look like or where would it be? I thought I knew all the parts by now.
It also says a few lines earlier, "No-drip nozzle adapter provides positive fuel cutout to prevent fuel odor and soot problems in the house." No mention of ducts here, but still. Are they only referring to combustion gases escaping through the observation port or the barometric damper? Or do they have the ducts in mind?
Thanks.
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