[67ChevyRedneck]

Fortunately, I was 100% aware of that, I read about a lot of horror stories from others on the net from dust build up. System was shut completely off during all sanding. I also wrapped a garbage bag around the filter and pushed it back into the hole, which made a snug fit. The floor was cleaned every night so it couldn't suck dust off the floor too. I spent a long time thoroughly cleaning the systems over the summer, as they appeared to have never had it done before.

I learned A LOT about these systems after I realized our upstairs A/C didn't work right from the first time I turned it on, see pic of damaged unit on page 3, and I learned all about the condensers getting dirty and clogged and causing freeze up and all sorts of crap.