Contact H.E.P.A. Vacuum and rotary brush 17 Riser Exhaust Lines and all associated registers for all 112 apartment units. Negative Air Pressure H.E.P.A. Vacuum to be placed at the bottom of each line to collect dirt, dust, and debris that's being cable brushed and agitated from interior walls of exhaust lines. Cleaning methods and procedures completed to Industry Standards prior to replacement and installation of new exhaust fans.