What's are these bits of residue that drift down out of my ceiling vent?

May 21, 2009 8:31 AM

What are these brownish-blackish floaty smudgy bits that drift down out of my ceiling vent at work? Is the stuff dangerous?

We moved into a new (to us) office several months ago that I believe was built in the 1970s for whatever that's worth. Over my desk is one of those square metal ventilation grates/vents that takes up half the space of one of those standard rectangular acoustic ceiling tiles. Whenever the AC comes on, little bits of brownish-blackish-grayish... stuff... occasionally but persistently float down out of it. For example each morning I have to blow a light speckling of it off my desk, and it accumulates again by the afternoon.

The stuff is light enough to float down fairly gently and to be blown away easily, but it's not fuzz consistency. The bits vary in size from dust-sized particles to chunks that are about the size of the head of a pin, but 3-D, so you only very rarely actually see one drift down, but you can easily see them collect on the pale wood of my desk. If you pick one up, it turns into a smudge easily when you smoosh it. Its composition does not appear to be uniform, but rather slightly varied.

I've looked up what asbestos looks like, and unless there is a cajun blackened variety, it's not that. We had the exterminator remove some roof rats recently, but it's hard for me to believe that they could have shit so much in the HVAC system that this neverending supply of atomized shit could continue to rain down on me for months. It happens in other offices too, which makes me think it must be the disintegrating remnants of some kind of building material used throughout the ceiling or ventilation system.

I've found this and this, which sound similar but it's hard to tell. One of them might be my same thing once it gets wet.

So WTF is this and is it dangerous for me to be exposed to this every day? Since some of the particles are so small and since the vent is right over me, I have to assume I'm inhaling some of it. Inhaling any particulate isn't ideal, but some make you sick or kill you, so, you know. Looking for anyone who has experienced and identified this more so than guesses.

posted by Askr to home & garden (5 comments total)

Isulation? Used to have a job blowing insulation into attics, office buildings etc. Some isulation is ground up wood fiber (actually they grind up old books, among other things) and it looks like fluffy dust. If it is insulation, I'd say they have a problem with a hole/opening into their ventilation system and the insulation is being sucked in. If that's what it is, I doubt it's dangerous per se, but it is treated with fire retardant so you probably dont want to be snorting the stuff all day. Call the building manager and get it checked out.
posted by elendil71 at 8:52 AM on May 21

In my work building we have continuous black dust that is, I'm told, the result of the duct lining disintegrating over time. Your dust sounds different to me, but could it be a different kind of duct lining falling apart?

Things you can also ask about:
has the filter on the air intake for the building been changed recently - this is unlikely to be the source of your problem, but isn't a bad question to ask.
Can we install filters on the vents?

We took some A/C filters that happened to be left around and put them over the vents. They turn frighteningly black over the course of a month or two. Then again, this is a lab and we don't mind having 2x3 foot blue filters duct taped to the vents.
posted by sciencegeek at 9:09 AM on May 21

Call whoever maintains the building. Ick. Make them fix it. You should absolutely not have to tolerate whatever it is.
posted by theora55 at 11:42 AM on May 21

FWIW, I have the exact same thing in my office. And every other office in my building. Facilities "cleaned" the vent in my first office, but it made no difference. I've always wondered what it is as well, so while that doesn't help, at least you're not alone.

Installing some kind of filter might not be a bad idea.
posted by thejanna at 12:54 PM on May 21

If the ceiling is high enough, suspend an open umbrella or parasol from the vent to catch the stuff before it falls on you. If you get a pretty one, it will also look nice.
posted by 5_13_23_42_69_666 at 5:35 PM on May 21