Programmed filter

摘要

A filter is provided for a smoking tobacco product, the filter having one or more channels which by-pass the main body of filtering material such that a portion of the smoke is caused to flow through the channel and a relatively short portion of the filter in the earlier puffs, while essentially all of the smoke flows through the main body of the filtering material in later puffs. Through the gradual change from a portion of the smoke flowing through the channel to all of the smoke flowing through the main filter body, the filter accomplishes a nearly uniform per puff delivery of total particulate matter, through a relatively steady increase in filter efficiency.