Along with the many visible to the eye asbestos containing building materials such as transite siding and panels, floor tile, plaster, HVAC duct wrap, acoustic ceiling tiles, etc., asbestos can be applied to some not so obvious places leading you to a good game of hide and seek.  A couple key materials that can fall into this category would be waterproofing, vapor barriers, and fire proofing.  Identifying these locations of hidden asbestos can save you thousands of unexpected costs by discovering them up front versus in the middle of a demo project or worse yet, not until after or at the landfill.  

The above photo is an example of hidden black waterproofing that was applied to concrete columns on the the exterior side only where it was hidden behind a brick facade.  It was found and tested by a 3rd party inspector before demo began and luckily was not asbestos.  If it ended up being asbestos and these columns were ran through a concrete crusher the entire pile would have been asbestos contaminated per the governing body (DNR in WI) leading to thousands of dollars in disposal costs not to mention the loss of the crushed material that was intended for backfill.