Question: I recently saw a mezuza on the entrance to a lift, though we don’t have one in our office. Do we need to attach one?
Answer: The Shulchan Aruch (YD 286:11) writes that one doesn’t need to affix a mezuza to a room on a boat. R’ Yitzchak Yaakov Weiss (Minchas Yitzchak 4:93) writes that there is a machlokes as to whether this halacha would apply to all moving rooms or not. Accordingly, there is a machlokes as to whether one needs to affix a mezuza to a caravan or not (See Minchas Yitzchak 2:82).
While rooms smaller than four amos by four amos don’t typically require a mezuza, the Teshuvos Chamudei Daniel holds that when such rooms are typically so small, they do require a mezuza (See Pischei Teshuva, YD 286:11; Yechave Daas 4:51).
Based on this, R’ Weiss writes that ideally one should place a mezuza on a lift. One should only place it on the lift itself, and not at the entrance on each floor.
Nonetheless, R’ Shlomo Zalman Auerbach (Minchas Shlomo 2:97:23) and R’ Moshe Stern (Be’er Moshe 2:88) disagree, writing that lifts are used for transport and cannot be considered a residential room. Likewise, the doors to the lift are useless doors once the lift has moved to another floor. Thus, a lift does not require a mezuza.In conclusion, while there are those who are particular to do so, the general custom is not to affix a mezuza to a lift.