Required emergency escape and rescue openings shall
be maintained in accordance with the code in effect at the time of
construction and shall be operational from the inside of the room
without the use of keys or tools. Bars, grilles, grates, or similar
devices are permitted to be placed over emergency escape and rescue
openings, provided the minimum net clear opening size complies with
the code that was in effect at the time of construction and such devices
shall be releasable or removable from the inside without the use of
a key, tool, or force greater than that which is required for normal
operation of the escape and rescue opening.