Spraying cellulose insulation into the wall cavities. It looks like a dirty job, and it is! One guy sprays the insulation into the walls and it seems about half of what is sprayed drops to the floor. The second guy has a large vacuum hose and his job is to vacuum up all the insulation off of the floor. The insulation blowing machine is set up to recover this material, add new cellulose, and send it back for another trip. A third crew member has a rubber roller gizmo which lightly scrubs the bulky cellulose down to the plane of the wall studs. The 3 of them just keep working in a big gray cloud of dust.