How can I get rid of vinegar-like paint odor?

Question

A friend got a new apartment (5 floor building built in 2008). The walls and ceiling of the apartment were renovated a few months ago.

Unfortunately, the ceiling color (Flügger Flutex 2S) started to smell. The smell is "lying in the air" like vinegar or old socks. Very subtle but noticeable. I assume that either the new color got bad or the new color chemically reacts with the old undercoat.

A repaint was done: Primer and a completely new color applied (Ekocolor Eko 3). This removed the smell by 90 %.

However, a few days later the smell is slowly noticable again!

My guess: The wall absorbed the primer and the new color and now the smell can escape the wall again.

The question: What to do next?

A: Complete removal of the surface? That's a lot of work. There is no wallpaper, so sanding would take place on 50 m² of ceiling.

B: Using an ozone device in the entire apartment for a day. Hoping it destroys the smell particle. But I have read positive and negative things about it.

C: Paint over again - but with isolating paint

• I think anti-mould paint could have very good isolationg effects. Example "Anti-mould": https://www.amazon.de/Zentrallager-13401144-Schimmelblocker-Isoliergrund-Schimmel/dp/B0050G8RS6
• Or maybe a "Wet blocker". Example: https://www.amazon.de/0-75l-Molto-Feuchtblocker-weiss/dp/B00FSA4P4E

Doing C would be my suggestion. But I don't know which color to choose and also: Should another primer be applied before applying the color?

Can an experienced craftsman/painter can give advice?

Update:

I am certain now that it was the primer used for the walls/ceiling (and not the quality paint of Flügger). My solution was to buy (from Germany):

1. Primer: "Pufas Tapeten- und Anstrichschutz"
2. Isolation color: "Pufas Aqua-Deck Isolierweiß"

Which was pricy but covered the smell finally. 👍

Answer 1

I'm willing to bet they used a basic latex primer, which will do little or nothing about the odor. Take the time to buy the primer yourself and make sure it specifically lists "odor" as something it will work against. Most oil-based primers will handle odor (although they themselves contain a strong odor initially). There are also some newer products that are water cleanup that claim oil-based features, including blocking odors (Kilz says this product will do it but I've never used it myself).

Answer 2

This probably won't work as well since the walls and ceiling have been primed and painted again since the bad paint was used, but I found this recommendation from Old House Journal:

For paint that dries and still has a persistent smell, try washing the walls with a mixture of 1 part bleach to 10 parts water, then rinse with plain water and a clean sponge. Allow the walls to dry completely. Follow with an odor-sealing primer, such as Kilz (kilz.com) or BIN Advanced (rustoleum.com), a synthetic shellac sealer. You may need to apply two coats before repainting with fresh (unspoiled) paint.

I have used diluted bleach to clean surface stains like tobacco residue off residential walls and ceilings, but I am not sure how well it will penetrate your surface paint to neutralize the odor of the underlying paint. Some sanding may still be necessary.

One option you didn't mention (with good reason, because it's kind of a "nuclear option") would be to replace all the wallboard. You probably won't be able to do this cheaper than sanding everything, but it may be less labor-intensive (depending on how much sanding is necessary) and it's guaranteed to get rid of the bad paint smells and let you start over with good paint. I normally wouldn't consider that on a building as recent as 2008.