2010 ADA Standards for Accessible Design Pocket Guide
407.3.3 Reopening Device.
Elevator doors shall be provided with a reopening device complying with 407.3.3 that shall stop and reopen a car door and hoistway door automatically if the door becomes obstructed by an object or person. [S.H. 4.1.6(3)(c)(i)]
EXCEPTION: Existing elevators with manually operated doors shall not be required to comply with 407.3.3.
The device shall be activated by sensing an obstruction passing through the opening at 5 inches (125 mm) nominal and 29 inches (735 mm) nominal above the finish floor.
The device shall not require physical contact to be activated, although contact is permitted to occur before the door reverses.
Door reopening devices shall remain effective for 20 seconds minimum.