What to ask, and why
The last company used an ozone machine and it still smells. Why?
Ozone treats the air, not the resin on walls, fabric and ducts. Someone has to clean or neutralize the residue itself.
Can my painter just cover the yellow film?
Paint over resin tends to bleed through. Wash the walls first, and put a sealing primer on before the finish coat.
The basement was a former grow. Is odor the only issue?
Maybe not. Years of high humidity can leave moisture damage or mold behind. Get that checked before any deodorizing.
Can my family stay in the house during treatment?
Not for a whole-house chlorine dioxide treatment. Ask for the leave and return times before you book.
Should I get the cost in writing first?
Yes. Ask for a written scope and quote before any treatment begins.