A duct brush for cleaning air conditioning and heating ducts. The brush is made up of a flexible hose connected to a cleaning head. The head is constructed to open like an umbrella for cleaning large duct areas. The opening and closing of the cleaning head are controlled by a plunger at the end of the hose held by the operator. In an alternatively preferred embodiment, a multiplicity of separate hose sections are connectable to each other end to end to from a hose of any desired length.
