safety valve
relief valve
escape valve
escape cock
escape **

You were the safety valve, in case I needed to bring the whole thing down.

As a safety valve, to keep them from getting out of control.

One way to think of it is as a safety valve.

"Part of our responsibility is to be a safety valve for people who have not been heard from."

Until well into the 1980's, there had been a safety valve.

"The bottom line is that people want a safety valve."

If anything, the question is whether it provides enough of a "political safety valve."

But, he added, there is no insurance that the safety valve works.

"Do you think that will act like a safety valve, and hold back some of the flood?"

"Just the fact that it's there is an important safety valve."