safety valve

Noun

safety valve (plural safety valves)

1. A valve set to open at a pressure below that at which a container holding a gas, vapour, etc. (such as a boiler or pressure cooker), would burst, thus reducing the pressure; a relief valve.
   • Spun glass mattresses are used for lagging the boiler, which has three Ross pop safety valves on the front ring.1941 April, “British Locomotive Developments”, in The Railway Magazine, London: Tothill Press, →ISSN, →OCLC, page 173
   • [A]nd to show that there was no shortage of steam, Royal Scot, directly we stopped, blew off vigorously from its safety-valves steam that well might have been used in the cylinders in the interest of timekeeping.1959 April, Cecil J. Allen, “Locomotive Running Past and Present”, in Trains Illustrated, London: Ian Allan Publishing, →ISSN, →OCLC, page 185
2. (broadly) A valve set to close a container holding a gas or vapour to prevent excessive loss of pressure.
3. (figuratively) Any mechanism offering relief from physical or emotional pressure or tension.
   • […] I have often thought that it was a great error in our legislature when they consented to put down the public lotteries in England. I am convinced that they were beneficial, acting as safety-valves to the gambling spirit of the nation, and that their prohibition has been productive of much crime...1840, F[rederick] M[arryat], “Diary on the Continent. Chapter XIX.”, in Olla Podrida. […], volume I, London: Longman, Orme, Brown, Green, & Longmans, […], →OCLC, pages 205–206

   Synonyms:

   outlet, release

   1. (US, figuratively) A United States law, codified at 18 United States Code §3553(f), authorizing a judge to disregard mandatory minimum sentences for some criminals with few or no prior offenses.
      • Hernández additionally requested that he be given a two-level safety-valve reduction pursuant to U.S.S.G. § 5C1.2, which mitigates the harsh effect of mandatory minimum sentences on certain first-time offenders who played only supporting roles in drug-trafficking schemes and who provided testimony...2020 June 30, David Jeremiah Barron, Circuit Judge, United States Court of Appeals for the First Circuit, “United States v. Hernández-Hernández”, in Federal Reporter […] (No. 19-1123), volume 964...