Chemical Exhaust is one of the few companies in California that can actually lower a technician inside your multi-story vertical ducts or stacks to insure a complete cleaning of the walls of the duct. We’ll rig a bosun chair at the top of the stack/duct, insuring that we meet all confined space requirements, and will then lower the worker who will scrape and/or vacuum the sides of the duct as they descend. In this manner all of the grease, lint, dirt and debris is removed from the sides of the duct. Our experience includes regular periodic cleaning of 25+ story vertical ducts. Ask your current cleaning company if they can do that!