Suspect mold inside walls, now what?

[leakyduct]

A room adjacent to a shower stall started to have an odor and if I stay in this room for long, my throat starts to hurt/burn.

The shower, which was tiled by a sloppy contractor, may have a slow leak, slow enough that no water stain shows on the ceiling below, but enough to create a moist environment for mold to grow in the walls. The odor I'm smelling may be mold related. I'm going to stop using this shower.

I also spotted ants coming out somewhere behind the shower walls, further adding to my suspicion there is rotting wood.

I thought about getting mold air sample. However, if the mold is inside the walls, what I'm smelling may not be mold spores but maybe neurotoxins emitted by the mold. I think air sampling only detects particles like mold spores, not poisonous gas.

What is the next step to take? What kind of contractor should I hire to figure this out?

I'm in the WA state in case you have location specfic comment.

[HVAC_Marc]

Tear out the walls and LOOK

[perfectionist]

A room adjacent to a shower stall started to have an odor and if I stay in this room for long, my throat starts to hurt/burn.

The shower, which was tiled by a sloppy contractor, may have a slow leak, slow enough that no water stain shows on the ceiling below, but enough to create a moist environment for mold to grow in the walls. The odor I'm smelling may be mold related. I'm going to stop using this shower.

I also spotted ants coming out somewhere behind the shower walls, further adding to my suspicion there is rotting wood.

I thought about getting mold air sample. However, if the mold is inside the walls, what I'm smelling may not be mold spores but maybe neurotoxins emitted by the mold. I think air sampling only detects particles like mold spores, not poisonous gas.

What is the next step to take? What kind of contractor should I hire to figure this out?

I'm in the WA state in case you have location specfic comment.

Do you have a thermal camera or know someone that does? There is a good chance that you may be able to find a slow leak that way, the water will be colder because of evaporation.