Measure the dimensions with a metal ruler that has graduations in millimeters.

The equipment cooling system has low flow detectors to give a warning when there is not sufficient cooling airflow. On the ground, the crew call horn sounds when low flow is detected in the supply system.

The fans are single-stage fans with an integral induction motor. They each have a check valve and install as a unit.

The supply and exhaust fans install with V-band clamps. Arrows show the correct direction of flow. The supply and exhaust fans are interchangeable.

The recirculation system uses a fan to move air from the passenger compartment to the main distribution manifold. This system reduces the amount of air necessary for the packs to supply.

Gas pressure in the sense tube holds the fault pressure switch in the closed position. The other two pressure switches close when the gas pressure increases because of an overheat or fire condition.

The ventilation system uses differential pressure to pull air out of the airplane. The air moves through overboard vents from the cabin galley and the lavatory areas.

When the entire storage area is full, new fault data, i.e. data for the current flight leg, will replace/overwrite the data for the oldest flight leg in the fault history.

The RESET test switch is used to erase the fault history. Push the RESET switch while the VERIFY and the green GO lights are on.

Outlets along the side walls and the center of the ceiling divide the air for symmetrical supply.

L1 entry door number 1 floor panel has a 1-inch notch 6 inches from the forward right edge.