I usually don't look for cover, or start building a sandbag bunker, unless I bottled the beer with a gravity above 1.015 ish. If you took a gravity reading, and it's 1.015 or lower, you probably
don't have anything to worry about.
Disclaimer text: That's just my general guideline. I have been found, on occasion, to be completely wrong. If you suspect bottle bombs, please wear protective eyewear, gloves and ass-less chaps. (WTH? Did I say that?)