In this question about turning off carb heat just before landing, one of the justifications for doing so is to reduce the likelihood of ingesting dirt into the engine.
How does carb heat (or the lack thereof) affect the amount of dirt that might be ingested into the engine?
I am not a pilot, but I would think there would be some sort of air filter like there is on a car/truck. Also, I would think that, if anything, ice in the carb (while Not Good™/potentially fatal, especially on landing), would reduce the likelihood of getting dirt into the carb by acting somewhat like a filter - i.e. giving dirt a place to land before making it all the way through and into the cylinders.