Heating Help

where do you shop for IAQ testing supplies?

is there a reputable national web site or catalog who is the best?

 specifically looking to test for airborne molds.

Testing gear

There are a number of sources.  Most manufacturers sell thru distributors, so your usual source of heating supplies may be your best bet. The same ones who carry combustion analyzers may also have access to the toxic/combustible lines as well, for example, Bacarach & Bendix.  Mold testing is different.  There are several test methods.  Some count spores. Others use samples, which are grown & identified under laboratory conditions.  That is the realm of the Industrial Hygienist or Environmental Engineer or Biologist, who have such facilities available.  The "mail in " tests that are sold at retail have a purpose as screening tests only, for proper mold identification, you need a trained person, with the proper lab equipment.
Another source for toxic/combustible monitors is the Conney Safety Equipment catalog, www.Conney.com, a general saftey gear mail order house.