The suit pings a proximity sensor, not an alarm, at Nita's approach, but Pepper can't hear it. The armor might be resonating with the sound, or might simply be vibrating, or something else, she's not sure and it doesn't matter.

It takes her longer than it should to remember she can get out of the suit, even just the helmet. Pepper drags it off her head and drops it, gasping at the relief of open air. The tone is still sounding but this is better, she might be able to think like this. Maybe. Give her a few minutes to breathe and get her head on straight.