Or using bleach as well is harmful to the good bacteria that the system needs.  

I would also change out the furnace filters and give the place a good cleaning with a mild bleach solution first.

A good ratio of bleach to water mix is 100% bleach, 0% water.

If mold, if it’s minor brush bleach on it, let dry, paint.

Previous owner cleaned and bleached the inside of the refrigerator, however, the freezer still has a mildew smell.My thoughts are that mold spores had traveled through the entire refrigerator when the electricity was turned back on and the fan resumed running.

I snapped it up for 50k, and we went to Lowe's and bought 6 gallons of bleach to shocked the well... rented it for years with zero cash in the game, and netted over $104,000.00 when said and done.Plenty more stories, but I'll leave room for others!

Example: I sold 2 of the 3 comps within a mile for 119K and 116K, this one is going to list for 85K, To get it up to the level of the comps, interior paint, some carpet, good solid bleach clean, laminate counters (area supports that decision).

Let me ask you something: if a dude with a perfect manicure and bleach teeth came up to you and promised you that you could make huge money renting out portable toilets for construction sites and outdoor events, you might believe him if his numbers were convincing, right?

They wanted something like $3K for the hazmat team to clean it up so we just bought a ton of bleach and rags and went to town.

Every month I go into a rental for "scheduled maintenance" to change AC filters, bleach out AC condensate lines, flush water heater T&P valves etc...one thing I do is to exercise open/close of all stop valves.