Well I've just looked this up. Seven people claimed to have "seen gun smoke" in the vicinity of the grassy knoll. Just one person "smelled" gun smoke.

Then you have failed to look it up.

2
Multiple Witnesses Smelled Gunpowder At Street Level

At least seven witnesses testified that they smelled gunpowder at street level immediately after the shooting.
Billy Martin was a Dallas police officer who was driving his motorcycle just behind the Presidential limousine?s left rear fender at the time of the shooting. He is on record as stating: ?You could smell the gunpowder?.?.?.you knew he wasn?t far away. When you?re that close, you can smell the powder burning?.?.?.you could smell the gunpowder?.?.?.right there in the street.?
Senator Ralph Yarborough, riding with Vice President Johnson in the second convertible, claimed to be able to: ?smell the gunpowder from the assassin?s murder weapon.?
Elizabeth Cabell testified that she was riding in the third or fourth car behind the President?s limousine when the shooting occurred. She had this to say: ?It was in just a fleeting second that I jerked my head up and I saw something in that window, and I turned around to say to Earle, ?Earle, it is a shot,? and before I got the words out, just as I got the words out, he said, ?Oh, no; it must have been a?.?.?.? [then] the second two shots rang out. After that, there is a certain amount of confusion in my mind. I was acutely aware of the odor of gunpowder.?
Tom Dillard was a press photographer riding well behind the Presidential limousine. At the time of the shooting, Dillard?s vehicle was still approaching the Texas School Book Depository Building, facing Oswald?s sniper position. He stated: ?I very definitely smelled gunpowder when the car moved up at the corner.?
Virgie Rackley was a bystander close to the street in front of the Depository Building who, after the second shot, smelled gunsmoke.
Earle Brown was a police officer stationed on top of the overpass under which the motorcade passed after the shooting. At the time of the shooting, Brown was looking north toward Dealey Plaza and the Depository Building. In his testimony he stated: ?I heard these shots and then I smelled this gunpowder?.?.?.It come on it would be maybe a couple minutes later so?at least it smelled like it to me.? Officer Joe Smith also reported, ?a distinctive smell of gun smoke cordite,? as he rode along Elm Street.
According to the House Select Committee on Assassinations (HSCA), measurements taken at Love Field , 8.5 kilometers (5.3 mi) by road from Dealey Plaza, found that the wind on the day of the assassination was blowing at around 24?32 kilometers per hour (15?20 mph) from the west-northwest.
http://listverse.com/2014/06/08/10-reasons-jfks-death-might-have-been-an-accident/