Asbestos and lead are heavily regulated industries. Inspectors must be licensed by the state. Check out the Maryland Department of the Environment websites for updated lists of inspectors. The link to the asbestos section is
http://www.mde.state.md.us/Programs/...stos/index.asp
The link to the lead in paint section is
http://www.mde.state.md.us/Programs/.../inspector.asp
There are NO regulations for mold/biological contamination.
Look for companies that have certified industrial hygienists or experts in microbiology who can explain to you what the findings mean. If an inspector wants to take samples, request viable mold spore/colony counts in AIR inside and outside the building. The outside sample is the reference sample. Wipe samples and vacuum samples tell you what is on the surface. It does not tell you what you are actually breathing. And remember, 1 colony of mold on a petri dish does not mean you have a sick building! Mold spores are everywhere.
DIYers -
Visually inspect for active water infiltration or water damaged materials. If water damaged areas are cleaned up and dried out within 48-72 hours, there is little likelihood of a mold growth problem. Common household bleach (1:10 solutions) or other household disinfectants work fine for cleaning up mold/mildew problems. For the big mold problems, most of the asbestos contractos also clean up mold since they have the equipment already.