open, screen emergency exit window for ventilation?

no frame, but just velcro and screen fabric that you can stuff in a hole when not in use, or leave it up all the time.
On my door, that has no screen door. I used "door screen" that has two pieces, with magnets to close the halves, and all that is held to the frame with velcro. To go thru the door the magnets release easy and click back together when they flap back. Keeps the bugs out and is easy to pass through.