Alternative for "Remain Open"

This is my first question on English SE. I'm rewriting a technical manual and I'm stuck at some terms which I'm going to ask here in the following days.

I'm trying to find a better alternative for the "to remain open" phrase. It's being used in a parameter name and if it's possible has to be expressed in the passive voice. The complete sentence will be something like "Steam Output Remain Open Duration". The current translation for this phrase is "Steam Output On Duration" which doesn't sound correct to me.

Any ideas?

PS: To clarify the situation I have to explain this parameter. It is the duration whilst the steam output remains open.

Speaking as an engineer, the existing translation is correct. You could also phrase it as "Steam Output Open Duration". Parameter names should be as short as possible.

As far as I can understand it, there can be no steam output when the passage is shut. I would, therefore, omit "remain open" and say only "steam output duration". It seems to be a specific subject and I may have misunderstood it, though.

"Steam Output should remain open for the [entire] duration."

or

"Steam Output should be kept open for the [entire] duration."