On the ASH-25 it is possible to confuse the air vent with the forward canopy release (used for bail out when you pull both front & rear releases). If the forward release is pulled in flight the front leading edge of the canopy lifts about 1" and the instrument panel drops about 1". The rear bayonet fittings will hold the canopy in place. This happened to me once and I was able to temporarily resolve the problem by removing my dress belt and looping it under my leg and over the release knob. That held the canopy front down until I got the machine on the ground. I later realized that the incident occurred because I was mildly hypoxic and very stupid. After 3 hours above 10,000' I got cold and pulled the "air vent" shut . . .
ROY