Um. Sort of. He actually dropped the control when Carissa screamed, which is making him feel incredibly stupid, and then fumbled it the first time he tried to switch it off before it occurred to him that maybe he was not supposed to do that, and then he switched it to low, sort of not wanting to waste the charge, and then he switched it off, but Carissa kept screaming for a bit after that.
He has been repeatedly told not to worry too much about the consequences if this sort of thing happens, and if everybody was just lying to him about that the entire time, Keltham can always just exit this universe by a sheer act of will, right.
"I'm okay if you're okay. Good Carissa."
"Figures that the first thing on this list which actually works is one with charges and which now has only 11 charges remaining."