Remain in your shelter, despite the lack of air
From Create Your Own Story
"Dear journal, I've stayed in my control room for about an hour now. There's no air. I can barely write this, and I'm getting dizzy. Maybe I should rip down the plastic sheeting and get some air in here. I should..."
The journal cuts off abruptly as the author succumbs to suffocation. Three days later, a group of survivors find a corpse of the floor, next to a journal and a plastic-wrapped window. One of them retrieves the notes, and makes a point to read them back at camp...