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

They happen when water treatment works become overwhelmed, usually after rainfall, allowing highly diluted sewage to spill into a river as a "safety valve".

From BBC

Dot plots and macro projections serve as a pressure safety valve where disagreement can be hashed out, without harming the consistency of the policy message.

From Barron's

The safety valves are drained, reserves are lower — and your money-market fund is the first domino.

From MarketWatch

The control room sent a message to the emergency response center requesting more batteries so they could open the safety valves and vent the extra steam.

From Literature

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