Proving a tenant is smoking inside

[Brynden Noble]

I’ve been getting complaints from one of my tenants in a triplex claiming she smells cigarette smoke in her house. She claims that the smell only occurs when the guy renting Unit 1 is home. His unit is directly underneath hers. Of course he promises he’s not smoking inside...I’ve done a walkthrough of his place while he’s not home and wasn’t able to determine if he’s actually smoking inside..I’m wondering if there is anything I can do specifically to prove that he is/isn’t smoking inside? Any tips? I’m planning on having my maintenance guy come and check on all things electrical and HVAC to make sure the smell isn’t related.