safety valve

American  

noun

1. a device that, when actuated by a gas or vapor pressure above a predetermined level, opens and allows the gas or vapor to escape until its pressure is reduced to a pressure equal to or below that of the predetermined level.

2. a harmless outlet for emotion, tension, etc.

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safety valve British  

noun

1. a valve in a pressure vessel that allows fluid to escape when a predetermined level of pressure has been reached

2. a harmless outlet for emotion, energy, tension, etc

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Etymology

Origin of safety valve

First recorded in 1805–15

Example Sentences

ObamaCare could soon became a safety valve for underwater cities.

From The Wall Street Journal

Banks have more regularly tapped a Fed lending facility designed as a safety valve that lets them exchange securities for reserves, offering another sign of reserves becoming less ample.

From The Wall Street Journal

In that incident, the board’s investigation found multiple safety failures, including a severely eroded safety valve that allowed flammable gases to dangerously seep into unwanted areas.

From Los Angeles Times

A safety valve had been removed from the pipes for maintenance.

From BBC

Elon Musk thinks humankind’s only safety valve is to move multitudes to Mars.

From Los Angeles Times