Sequencing with the HVAC contractor
Order matters: abatement, then a clean-and-inspect step, then the HVAC crew. Positive insulation can turn friable once it is cut or torn, so it is wetted and removed in a negative-pressure enclosure or with glove bags. The waste is sealed and labeled, and an EPA-licensed hazardous waste transporter carries it.
Different agencies draw different lines. The district asks for notice at 100 linear feet or 100 square feet of regulated material; duct is counted in linear feet, which can bring a job to that line early. Cal/OSHA registration for contractors starts at 100 square feet, and smaller jobs still carry worker-protection duties. Access, attic or crawlspace height and the extent of replacement shape the cost.
Where sprayed ceiling texture surrounds a register opening, duct work meets asbestos popcorn ceiling removal. All other services, and the rules behind them, are on the Hayward Asbestos Removal homepage.