A filter is designed to reject some substances, while permitting others to pass through.

VOA: special.2010.01.05

The original design of the ceramic filter came from a chemist in Guatemala,Fernando Mazariegos.

VOA: special.2009.06.22

These holes let water slowly pass through the walls of the filter.

VOA: special.2009.06.22

In simple terms, think of snow or ice as a filter.

VOA: special.2010.01.05

Tests have shown that the filter produces safe drinking water.

VOA: special.2009.06.22

The water filter costs little to make.

VOA: special.2009.06.22