Mechanical equipment as source of contamiants

I thought I had commented, but apparently not. With regard to legionella, I would say that between good design and good maintenance that should be covered. The IAQ credits are primarily focused on outdoor air through intakes and interior sources of potential contaminants like cleaning supplies. The short answer is no, in my opinion cooling towers and chillers are not mentioned specifically, and are outside the scope of this requirement.

As for soiled utility I'm not sure what that refers to. All I can think of is soiled linen areas. Where are you seeing that?

I agree with Michelle on the towers. The cooling towers are covered in the WE section and I've never seen anyone apply cooling towers to this credit.

Soiled Utility is generally required to have a door closers, neg pressure and may be fire rated. They can contain chemicals that may fall under this credit. But they can also be holding for dirty linens, garbage and recycling. It depends on your user so you have to ask.

Although not explicitly stated, this credit primarily tackles airborne contaminants. Legionella is a waterborne contaminant that only becomes an airborne contaminant when it becomes aerosolized, e.g. at a decorative fountain. It is far more important to address legionella potential at the source, as Michelle describes, than to address it through the mechanisms outlined by this credit.