Why would you need gas masks? What analysis demonstrates there’s a risk that such things would address?

Respond to clear risks that have strong analytical backing and urgency. Don’t let your own fear drive decisions.

For example, when driving I don’t worry about a large truck 2 miles ahead of me, but rather the vehicles close to me, and I keep an eye on vehicles a little farther ahead and behind me.

I do try to keep vehicles filled, but that’s as much for convenience and risk aversion: I’ve had to do a longer drive at the drop of a hat, and sit in traffic for bad weather or accidents.