Welcome to outdoors.SE! Older buildings often contain asbestos in solid form, and it may be sealed up (under floorboards, in tape around heating ducts, etc.). As long as it's not ground up into dust, the hazard is minimal. For example, construction workers knocking down a building or remodeling it can get exposed to asbestos dust if they don't realize that there's asbestos in it. Simply walking around in a building that contains undamaged asbestos isn't dangerous. The danger would be greatest for people who have long-term exposure, e.g., the people who used to work in the asbestos industry. You could try to judge whether the building is damaged, but it might be difficult to figure that out.