| 摘要 |
A smoking article (10) comprises a tobacco rod (15), a filter unit (16) having a substantially circumferential ventilation zone (24), and a tipping paper (22) joining the tobacco rod and the filter unit, at least one side of the ventilation zone being bounded by a substantially circumferential element (28) having a greater outer diameter than the outer diameter of the ventilation zone. Protection is gained against inadvertent or deliberate blocking of the ventilation zone by defining a recess for the ventilation zone. Using a range of materials with controlled porosity and diffusion attributes within the recess enables lower smoke yields under high puff volumes (flows) to be achieved as well as a decrease in the level of selected smoke components such as carbon monoxide.
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