Mezuzahs on bomb shelters
Millions of Israelis are spending much of their time in bomb shelters these days. Do these rooms in basements and underground require a mezuzah?
We are commanded to inscribe the words of the Torah "on the doorposts of your house and on your gates". From here, the sages learn that a mezuzah is only for a space that is fit for dwelling. Our shelter has an old TV and a loo, but otherwise it's bare concrete and you wouldn't want to spend a lot of time there.
Storerooms fall into a grey area. We do not live in them and yet pop in and out of them frequently. So the rabbis rule that you should affix a mezuzah on the doorway of a storeroom but without making the blessing for the mitzvah of mezuzah. Rabbi Ovadia Yossef ruled since that a bomb shelter is only ever used in case of an enemy attack (hopefully not a frequent occurrence), and remains empty the rest of the time, it does not require a mezuzah.