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First time home owner here. I stuck these vent deflectors a month ago on one of our vents and I removed it today for some other reason. I noticed these stains that looked like water stains but I think it's actually something that is growing - maybe unfortunately mold or something. I need help in understanding this situation and possibilities of this happening. Please share your experience or knowledge related to this issue if you can.
Thank you!
EDIT: Mystery solved - this seems to be the result of some chemical spray during cleaning. Not concerning.
It could be a couple of things that I am aware of.
Dust would be the most obvious. Many plastics can hold a static charge and dust can stick to it. The pattern looks "splotchy", so if not static electricity, it might be oils or some other kind of chemical that is mildly sticky. (Injection molding can sometimes use release agents during manufacturing that are rarely cleaned off. Don't eat random bits of injection molded plastic, kids.)
Simple moisture could be the issue as well. If you have been using your air conditioning, it'll get the plastic cold and water can condense on it. Dust or something else might be sticking to it. The water could dry, leaving behind the dust and obfuscating the root cause.
While it could be a mold of some kind, it doesn't look too much like it. That would point to existing mold in the ducts that is sporulating. Those kinds of house molds are usually dark and nasty, not white. White house molds exist but I suspect it's region specific as to what kind would grow where you are at. (I grow mushrooms, so I have a supply of petri dishes I would test that substance on, TBH.)
Just for good measure, check your air filters. It's something you need to do anyway and if they are nasty or old, you could be circulating excess dust in your house and it's a sign the filters need to be changed. Air filters are functional! Air conditioner heat exchangers can get clogged and, depending on the type of unit you have, be somewhat costly ($500-$1500) to clean properly. I have paid for this procedure twice before I found out that the air filter assembly is garbage in my unit.
Is the substance oily or powdery? If you clean it off, how long does it take to come back? Did someone spill something near that register that you weren't aware of? Were the carpets recently cleaned?
I am sure that HVAC people may have a more direct answer, but that is my list of things to check.
It's the splotchy pattern that is bugging me though. It's highly unlikely that something is getting sprayed out of the air ducts, other than small quantities of water condensation.
Thank you so much for going so detailed! That is so much good information and brainstorming. I washed it with soap - it still stays, I doesn't go away or even reduce a bit.
Spray - possible. My cleaning people come over once every two weeks and clean windows and blinds as well. This vent happens to be right above a window.
I also run a humidifier in the room at night. No other room has this much gunk on it. Only my room does. So that could be one more contributing factor.
The substance is not oily. It is not powdery either. It seems like almost etched into the plastic - this may support your spraying theory: someone cleaned something nearby with sprays that could damage acrylic surfaces.
That was a good investigation! Awesome person you are!
If it's etched, it's chemical damage. Just from my 3D printing alone, I know that common chemicals (generally acetone or various alcohols) can easily damage and melt some kinds of plastics. So, I agree. I think we found part of the puzzle.
And you are welcome! Thanks for letting me spew out theories.
I believe chloroform works well on PLA...
I didn't know that. Chloroform always helped my girlfriends melt into my arms, but I never thought about its use on PLA. (Huge /s for people who think I was serious.)
While I was googling around about chloroform smoothing, I also stumbled upon ethyl acetate as a smoother for PLA. It's probably better for your internet search history to go that route instead. I have a ton of weird shit for my engineering fascinations, but a bottle of chloroform would probably be at the top of that list.
The shape of the stain and the spread of the dots look a lot like a spray to me. The large stain is where the centre of the spray hit, the smaller dots are where it misted out / splashed from the centre, and the neat clear line across the middle looks like the front of the acrylic piece protected part of the back / inside because of the angle of the spray. If it's mounted the same way up as you're holding it in the photo, it would make sense based on someone spraying upwards towards the top of the window.
As remotelove said, some chemicals can damage plastics, and that's what I think has happened here.
Sounds right to me. Mystery solved.