A mezuzah should be affixed to a room each side of which measures at least 4 cubits (approximately seven feet);
If one of the walls of the room is less than seven feet (and wider than one-and-a-half-feet) but the area has at least 36 sq. feet, the room requires a mezuzah which should be affixed without a blessing;
A walk-in closet which has the above minimum dimensions requires a mezuzah without a blessing;
A walk-in safe requires a mezuzah; however, a walk-in refrigerator does not;
It is a wrongly believed that only the front door requires a mezuzah. If a house has many entries, there is an obligation to affix a mezuzah to each one of them, even if they are not used.