White Powder on Walls

This home is from late 70’s early 80’s. White residue all over walls in living room and downstairs hallway.

A restoration company cleaned up a flood in the home last year. Three months ago white residue started showing up.

Moisture levels extremely low (<10% in all drywall throughout the home).

Furnace filter dirty with white material.

Suspect drywall/construction dust however the restoration company came back and say I am crazy and drywall dust is less “gritty” than this stuff.

Have collected samples and processing this week.

Any ideas?

Is there any construction or major demo work being done in the area .check for outside contamination

Hi David, This is just a question so I can learn something from this. You mentioned you took samples and are processing them. How did you collect the samples and how are they being analyzed?
Seems odd it is only in those two areas. I was on a job a few years ago and in three rooms they had done some drywall work. When they were done the painters finished their work. Last thing that was done was a thorough vacuuming of the carpet. The next day the customer complained of a fine white powder on the walls. After a lot of probing we found out the shop vac did not have a fine dust bag covering the filter. The carpet was covered with tarps during the drywall work but after the tarps were removed nobody vacuumed the carpet before the painters came in. There was enough drywall dust hidden in the carpet that came out with the shop vac and was then exhausted throughout the rooms and stuck to the paint. It was so fine it wasn’t noticed while they were vacuuming. It was the customer who merely ran their hand across the wall just to feel the finish of the drywall and then noticed the powder on their hands.
Please follow up with your post and let us know what you discovered.

No demo work nearby - rainy little neighborhood with no active construction

Hi Thomas,
Testing through environmental lab (usually I use for asbestos). Bulk and swab samples taken.
I like your idea re: shop-vac. One contractor that came out said it couldn’t be drywall dust as “it was too gritty”. However other junk in the vac could be added into the mix…

I have just running into the same problem in the entire house ,with this white power stain on the walls… what should I fix this… i am over whelmed and makes me worried… is it a health danger issue

I know this is an old post, but I just discovered this discussion. I’ve doing some reading about the phenomenon called “hazing” or “frosting” in which the calcium carbonate in the pigment of the wall paint itself sometimes separates from the paint and creates a white powder residue on the drywall. The only cure mentioned was to clean and reseal the sheetrock with a high quality primer and paint again. Does anyone have any thoughts on this? I’ve got this very problem in my own home.