Have a common problem where scissor lifts tend to drive over orange test sites.
1: does dirt in the sensor area affect the test?
2: would placing a vinyl traffic cone above test sites affect test results?
Dirt can be vacuumed or blown out of the sensor tube, usually with no problem.
Placing a cone over the test site is like placing a bullseye on something. They will hit it for sure!!! But seriously, anything that will disrupt or impede the drying of the slab will affect the RH in that area. So I would say placing a sealed 16" diameter rubber cone over the test site will hold vapor emissions and slow the slab's drying in that area. A small open top cone may effect drying a slight bit, but probably not enough to cause a noticeable difference.
I always try to put tests in locations that people aren't driving over the caps.