I recently needed to replace the AC blower fan on a 2010 Honda Fit because it started making some weird noises. I was curious if I can fix the noise adding some lubrication, so I removed the fan from the motor axle to see if I can drip a drop of oil somewhere. What I found under the fan was surprising and alarming. A thick layer of micro particles, obviously produced by the electric motor (carbon, copper dust?). To buy a replacement, I was looking at the prices and found that an OEM thing would cost about 10 times more than the after market item (roughly about $300 vs $30). Tough decision, so I thought maybe a middle way solution would be best option, so I bought an used OEM one. When I received it, first thing done was to check if it is clean under the fan. Unfortunately I found the same thick layer of dark dust. I am pretty sure this is an issue that anyone would find if checking (which is very easy, just pulling out the cover under the dashboard on the passenger side to expose the blower fan, disconnect the cable and remove 3 screws).
I consider this a health hazard, having those micro particles mixed in the air that is pushed into the cabin. I am also surprised to see this flaw overlooked by Honda. I would be curious to hear some thoughts about all these.

 

What do you think diesel exhaust is? Just send it, bud.

 

Clean it, and be done with it. Get a higher quality cabin filter. Mine looked similar to that from my 09 civic. The motor was making a lot of noise, and not serviceable, so I just tossed and installed an aftermarket one. I prefer the OEM one because the fan blade assembly is serviceable while the AM ones are pressed on, and not able to get off easily.