Atmosphere conditioning pump

From Memory Alpha, the free Star Trek reference

The atmosphere conditioning pump is a component of a starship's life support system. To prevent life support failure, atmosphere conditioning pumps are regulated by seven independent safety interlocks. If these interlocks fail, the pumps enter into negative mode and life support terminates.

When the USS Enterprise-D was hijacked by Data in 2367, he was able to set the atmosphere conditioning pumps on deck 1 to negative mode to terminate life support on the deck. (TNG: "Brothers")