The hazard
Asbestos is still in many older buildings, in insulation, flooring, roofing and other materials. Disturbing it can release fibers too small to see, and you can breathe them in without knowing it. Those fibers can cause lung cancer, mesothelioma and asbestosis, often many years later, and smoking makes the lung cancer risk worse. You cannot tell asbestos by looking at it, so if you are not sure, stop and ask.
The action
All Class I, II and III asbestos work must be done inside regulated areas, marked with warning signs and limited to authorized persons (29 CFR 1926.1101(e)(1), (e)(3) and (k)(7)(i)). Employees must not eat, drink, smoke, chew tobacco or gum, or apply cosmetics in a regulated area (29 CFR 1926.1101(e)(5)). If you see asbestos warning signs or plastic barriers, stay out unless you are trained and authorized. Where respirators are required, filtering facepiece respirators, the disposable kind, must not be used against asbestos fibers (29 CFR 1926.1101(h)(3)(i)(A)). (29 CFR 1926.1101(e)(1))
ASK THE CREW
Why are a broom and a regular shop vacuum the wrong tools for asbestos dust?
From the talk: Asbestos awareness. Read it in full, free, with the questions and the sign-in sheet.