[taregg (OP)]

i try it this before and it gives very little smoke .but does it give you less toxic for health.

[Bored chemist]

What is a vent cigarette?

[RD]

Q. "what happen if we smoke a vent cigarette"

A. smokers change the way they smoke to counteract the vents ...

... a smoker’s lips or fingers may block the air ventilation holes in the filter, leading to greater tar exposure

http://www.cancer.gov/cancertopics/factsheet/Tobacco/light-cigarettes

[taregg (OP)]

i mean a small hole vent above the surface of the cigarette .btween the filter and tobacco trunk cigarette..

[Bored chemist]

I thought that was what you meant, but I wasn't sure.
Anyway, RD is right.
The cigarette design was changed to fool the test.
The tests for tar and nicotine are made with a machine which has a cylinder shaped hole for the cig.
So when a machine "smokes" the cig, the smoke is diluted by the air through the vent.
but when people smoke them, the smokers lips cover the holes so the vents don't make much difference.
Also the smokers want the nicotine and, if they get less nicotine from one cig, then they will often smoke more cigs to get the same amount of nicotine.
That is good for the tobacco company, but not for the smoker.