hood vents
The little streamers need to be taped to the top of each vent, and short enough so they can swing into and out of the vent.
I was editing as you answered. Wouldn't it be better to attach the streamers under the vents so they are not overcome by wind passing over the vent? If the wind was coming from underneath it should force the streamers out the vents.
Taped to the top, (or the underside of the top, as you may mean), hanging down to cover the opening, but not dragging on the hood. The streamer would act like a flapper door, responding to direction of air flow.
Important for them to be out of the airflow across the hood...behind the vents.



