REPOST
Dear fellow forum-ers,
I have seen many air con units that have been "serviced" every 3 months and still look like the above photo.
I would recommend that chemical cleaning be done at least once a year and normal servicing / cleaning of filters every 3 months.
And by chemical cleaning, I mean that the air con guys will bring down the unit, take off the plastic covers and use their chemical to wash the cooling fins. and after they have done their work, look into the area where the air comes out, and if it looks like my photo, tell them that it is not clean enough.
And what will happen if your AC unit looks like in the photo? Mold will grow on the dust and dirt and every time you turn the AC on, the mold spores will go airborne, and will land onto whatever is in that room.... beds, tables, books, furniture, clothes and they will stay there till conditions are right, then they reproduce. (in fact, that is the perfect place for molds to grow and reproduce in, condensation / changes in temp (every time you turn and AC on and off))
Be Safe.