Does it appear sprayed on? On some exposed steel structures they use a spray on fire proofing that protects the steel from exposure and allows a little more fire retardation. It will make you sick when they spray it but is fine when dry. Probably should wear a mask when scraping it off just in case. Also if the building is old enough it could be Asbestos. Just because they say it's all been abated doesn't mean it has.
