Patent ID: 8453705

Claim:
A door to be selectively movable to a closed position, a barrier position, and an open position relative to a doorway of a wall, the door comprising: an upper section to be vertically translatable relative to the doorway along a track via a first roller attached to the upper section; a lower section to be disposed below the upper section and to be vertically translatable relative to the doorway along the track via a second roller attached to the lower section; and a selectively separable connection to be between the upper and lower sections to effect selectively, upon vertical translation of the upper section, one of the upper and lower sections being coupled together without separation or the upper and lower sections being uncoupled to enable separation therebetween at a predetermined location of the lower section, such that: a) in the closed position, the upper section may abut the lower section at an elevation where the upper section and the lower section can substantially close off the doorway; b) in the barrier position, the upper section is vertically spaced-apart from the lower section while retaining a connection to the lower section, to define a ventilation area therebetween, whereby the ventilation area enables air to pass through the doorway; and c) in the open position, the upper section and the lower section abut one another and are elevated to open up the doorway.