Emergency Exit

Question: Our landlord has extended our flat and has installed an emergency fire exit. As we hope to never use this door, do we need to affix a mezuza?

Answer: The Gemara (Menachos 33a) suggests that R’ Yehuda Hanassi used to enter the beis hamedrash through a door that had no mezuza because it was never used by anybody else (see Tur YD 286:18). Nonetheless, the Gemara (ibid. 34a) concludes that one must affix a mezuza even on a doorway that is rarely used.

The Shulchan Aruch (YD 286:17) writes that one must affix a mezuza to each door that is designed for regular use. If some doors are no longer used due to fewer inhabitants, one must not remove the mezuzos.

The Rema (YD 286:18) adds that this only applies to a door that is used for both coming and going. A small door that is only used for passing food through would not require a mezuza (see Kitzur Shulchan Aruch 11:1).  

R’ Avraham Dovid Wahrman (Mikdash Me’at 286:48) stresses that this only applies to a doorway that was designed from the outset to only be used in this manner. Once a doorway was used normally, it does not become exempt from a mezuza even if it is no longer used.

R’ Sholom Mordechai Schwadron (Maharsham 2:265) writes that if one has a door that one cannot use, one is exempt from affixing a mezuza to it. Thus, if one has a roof without a maakeh, one does not need to affix a mezuza to the access door.

R’ Shlomo Zalman Auerbach (Minchas Shlomo 2:100:5) writes that an emergency exit that can only be opened from the inside does not require a mezuza.

In conclusion, an emergency exit that is not used for non-emergencies does not require a mezuza.