To perform at its best this system needs regular cleaning.

But how do you tell when it needs cleaning?

A little girl who would not look down at her shoes before school, in case they needed cleaning.

And there never was a floor that didn't need cleaning.

George hadn't considered when he built this place that it might need cleaning.

I have a laundry list of things that need cleaning.

Owners must pay attention to the area around their eyes and mouth, this may need frequent cleaning.

But screens usually need cleaning, and sometimes repair, before another season's use.

Those that merely need cleaning and new windows could be closed for several months or up to a year.

Not all ceramic pieces are dry when they need cleaning.