14 CFR § 23.2315

With the cabin configured for takeoff or landing, the airplane is designed to:

Facilitate rapid and safe evacuation of the airplane in conditions likely to occur following an emergency landing, excluding ditching for level 1, level 2, and single-engine level 3 airplanes.

Have means of egress (openings, exits, or emergency exits), that can be readily located and opened from the inside and outside. The means of opening must be simple and obvious and marked inside and outside the airplane.

Have easy access to emergency exits when present.

Airplanes approved for aerobatics must have a means to egress the airplane in flight.