tenant complaining about musty smell in closet

[David Sisson]

I have a new tenant in my commercial property. They are complaining about a musty smell in a closet and have used the dreaded "mold" word. They are complaining about headaches. 

Honestly, this is their second day in the space. I suspect they are just tired from moving in, but who knows.

The building is old (renovated mill building/warehouse). We have been battling water problems, but no observed mold in the building. The closet does have a slightly musty smell, but not a major one. I occupied this space previous to this tenant, and none of my employees had an issue. 

I'm going to do a mold self-test, and see if there's further ways I can keep water away from this part of the building. Obviously, if there's a problem, I'll need to do something about it. 

Beyond that, what's my duty here? I really don't want to get a "mold remediation" company involved, because that sounds like "screw my insurance company for as much as you can" type of stuff.  

What's my duty here?