What is this phantom litter box smell?
July 18, 2014 5:41 PM   Subscribe

How can I eliminate (or mask) a weird smell in my house's A/C?

I recently moved into a very well-maintained townhouse and have been noticing a weird, faint, intermittent smell that seems to be coming from the vents as the A/C runs. It kind of smells like a litter box. I notice it most often when I'm hanging out in my master bedroom since I spend most of my time there, but have noticed it when I was in the living room, too. I rent this home, but would prefer to address this problem myself if possible, without involving the landlord. Any ideas for getting rid of this smell?

In case it's relevant:

- House is probably 30 years old, but in great condition (owned and leased by a contractor)

- I keep my house immaculately clean, and have no pets (but two kids)

- When I moved in I had the upstairs carpets cleaned and deodorized with some kind of anti-microbial additive (this was a month ago, so very unlikely it's anything to do with the carpets); I've also tried Febreezing my bedroom carpet and linens but that didn't help, nor have the plug-in air fresheners I've tried

- It's an end unit, connected on just one side, and my understanding is that the connecting neighbor is very particular about her house - no chance she's an animal hoarder or anything weird like that

- I keep my A/C running at all times, usually set at 69 degrees - I like it very cool and am also trying to keep the humidity down; I also run a dehumidifier in the basement

- Vents are located on the baseboards and the bedrooms all have ceiling fans which I've kept running most of the time

- House is in Maryland, so moderately warm climate right now (85-95 degrees in summer)

Finally, for what it's worth, the smell isn't super horrible, but enough that if I did have a litter box, I'd definitely be rushing to clean it. Also, I'm starting to feel a little paranoid when I have company in my bedroom - I spend way, way too much time cleaning my house for it to smell anything less than awesome!

Thanks for your help!
posted by justonegirl to Home & Garden (6 answers total)
I haven't tried them, but companies like clenair.com offer odor elimination products. My HVAC guy recommended it as a last resort for some odors I was trying to track down.
posted by PorcineWithMe at 6:16 PM on July 18, 2014

Are you sure you don't have mice running around somewhere? Rodent pee could cause the smell.
posted by Hermione Granger at 6:37 PM on July 18, 2014

Response by poster: I definitely haven't seen or heard any kinds of rodents! Although now I'll be thinking about them tonight... ;)
posted by justonegirl at 6:39 PM on July 18, 2014

Check, clean, and possibly replace any air filters or screens in the AC unit and HVAC system. Look in the returns, on the unit, and wherever else there might be a filter.
posted by carsonb at 7:59 PM on July 18, 2014

Get a blacklight flashlight and after dark, with all other lights off and all curtains closed, run it along the baseboards and the lower part of the wall (up to about 2 feet from the floor). And also run it over the vents themselves. If you see streaks, its likely biological and quite likely cat urine. A tough scrub and a product called Zero Odor* will save you if that's the problem.

If you see light streaks actually on the vents, pull the vent covers off and scrub them, plus inside as far as possible, and apply Zero Odor there as well.

Unfortunately, even really old cat urine from three tenants ago still smells like cat urine if untreated.

* I'm not affiliated with ZO, just a veteran of the wars they fight
posted by kythuen at 8:49 PM on July 18, 2014 [2 favorites]

Ugh, my first thought was rodents as well. It can smell exactly like the litter box smell you're describing. Id check closets and the edge of the carpets VERY carefully for rodent turds that may have otherwise been very fastidiously cleaned up.

I've been duped on this one before moving into a place...
posted by emptythought at 12:45 PM on July 19, 2014

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