Elevator hoistways are, in essence, wind tunnels. Constant airflow creates great pressure in these shafts. The only escape for it is through the hoistway doors when they open and close. A door operator on the elevator cab opens them, but the closing of the exterior doors is assisted by a reel closure. This is the most vulnerable point of the system. Air pressure rushes in and out trying to prevent closing, which usually prevents proper latching of the interlocks and keeps contacts from matching up. The result of this is a broken safety circuit; thus, failure to the elevator system and operation.
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