Nortel 7400 Hardware Installation page 459

A minor alarm, 'Hardware report = cooling unit', occurs when you
disconnect the cooling unit from an active shelf assembly.
3 Wait until the fan blades are no longer rotating before fully removing the
cooling unit.
4 With your right hand, hold onto the handle located beside the upper
airflow grill of the faceplate.
5 Pull the cooling unit out of its slot, making sure to support the underside
of the unit with your left hand.
6 Hold the unit so that you do not contact any of the copper-colored EMI
gaskets that are located behind the faceplate.
Multiservice Switch 7400 Hardware Installation, Maintenance, and Upgrade 6.1S2
Chapter 39 Hardware procedures 459