Air compressors were introduced

 Air compressors were introduced as a more effective alternative to portable blowers. The use of skippers or snakes, which moved through systems with compressed air to assist in air washing air ducts. • Compressed air-washing and vacuuming are now sometimes augmented by manual scrubbing with brushes and flexible rods and whips and can assist in cleaning hard to reach dirt buildups in air handling systems. Where ducts are lined with fiberglass insulation, this treatment could damage the insulation and release fiberglass fibers to further contaminate air. • The use of HEPA filtration can be used to trap very small particles. This might be important for commercial duct cleaning where equipment exhaust stays inside a building, but offers little for residential duct cleaning where filtration equipment is placed outside. • For truly contaminated duct systems professionals can cut into the duct work to insert the vacuum line to remove localized dirt build-up. Some commercial air duct cleaners are equipped with tiny fiber-optic cameras to assist in locating dirt build-up and to confirm cleaning effectiveness.