How do they unclog mail chutes in skyscrapers?

I've thought about that myself whenever I see a mail chute. Maybe they throw a small bomb in it to unclog it? Have no clue. lol hmmmmmm..just thought of something. Maybe they use a roto-roter type device kinda like a plumber would use to unclog drains.

Hi. Maybe they hire little people to slide down in there, and use there feet to clear the chute, that would unblock and do the job for sure lol... Well Im going to agree with the person that said, maybe they blow air down there, at certaint intervals, and use censors to detect the blockages... Look Im only guessing, I have no idea...

Never even occured to me. Hmm. How did you ever come up with this? Where I live there are not a lot of skyscrapers so maybe I am not thinking enough about them. Is this really a problem skyscrapers often have?