[Las Vegas Dave]

...if the window and door are sealed, won't the air run out?

Chemical or biological WMD would be air born and flow with the wind, minimizing one's exposure and the need for extended sealed shelter.
I suggest you get a RX from your Dr. for cipro and keep close by, and also check for the closest routes to local medical facilities, (I am 1.3 mi. to local hospital).

[oceanperch]

I keep a combo of Cipro and Flagyl on hand due to frequent colon infections got that covered.

[Mamzelle]

A Las Vegas hospital, with Las Vegas Emergency personnel?