He also said that teeth should be cleaned periodically by a dentist.

All power tools should be cleaned periodically.

To solve the dust problem, some models are fitted with dust filters but these must be periodically cleaned.

To keep water treatment filters functional, they have to be cleaned periodically to remove particulates.

Their runways are periodically cleaned of waste, which is donated to local farmers for fertilizer.

These accumulations of lint will block the airflow so the duct must be cleaned periodically.

"If you have them cleaned periodically, they'll never get that bad," he said.

But they were aware that sediment was collecting and that leak technology wouldn't work if the lines were not periodically cleaned.

The cooler itself needs to be drained too, as well as cleaned periodically and the pads replaced.

The filter must be cleaned periodically.