Question: May one inflate a rubber air mattress with a non-electric pump or by mouth on Shabbat?
Answer: The Gemara (Shabbat 48a) states that one may not stuff a pillow with cotton or feathers on Shabbat. This means that if one has a bag of feathers as well as a pocket-like cloth (the pillow cover), the feathers may not be placed into the pillow cover on Shabbat, for this constitutes the prohibition of “repairing a vessel” on Shabbat.
The Gemara continues and states that Rav Chasda allowed stuffing a pillow with feathers on Shabbat. The Gemara explains that there is a difference between an “old” pillow and a “new” pillow. Regarding a brand new pillow which never contained feathers before, placing feathers into the pillow constitutes the prohibition of “repairing a vessel” on Shabbat, for until now, no pillow existed and now, after the individual’s actions, a usable pillow was created. On the other hand, regarding an “old”, pre-existing pillow which already contained feathers and some of its contents merely fell out, one may return the feathers into the pillow on Shabbat.
Maran Ha’Shulchan Aruch (Chapter 340, Section 8) rules likewise: “Pieces of cotton and the like which fell out of a pillow may be returned on Shabbat. Nevertheless, it is forbidden to stuff a pillow for the first time on Shabbat.” This is based on the above distinction between a new and old pillow.
Based on the above, the Poskim discuss the law regarding inflatable mattresses or pillows made of rubber (or plastic or other synthetic materials) which were inflated once before the onset of Shabbat and over the course of Shabbat, it has lost some air. Is it permissible to re-inflate these objects on Shabbat or not?
Maran Rabbeinu Ovadia Yosef zt”l writes (in his Chazon Ovadia-Shabbat, Volume 5, page 342) that an inflatable pillow is comparable to the law regarding the pillow discussed in the Gemara and thus, as long as it was inflated once and worthy for use as a result, re-inflating it will not constitute a prohibition of “repairing a vessel” on Shabbat and will be permissible. He writes that Hagaon Harav Shlomo Zalman Auerbach zt”l and other great Poskim rule likewise.
Although Hagaon Harav Yosef Shalom Elyashiv zt”l ruled stringently on this matter because the act of inflating is a mundane action reserved only for weekdays and thus should not be performed on Shabbat, nevertheless Maran zt”l rebuffs his opinion based on the words of the Rambam in his response (Chapter 64) “that it is clear to anyone who understands that you shall never find anything forbidden as a result of being a ‘mundane action’ if it is not an action that can lead people to perform an actual forbidden work.” Maran zt”l quotes other Poskim who discuss this matter and therefore rules leniently on this matter as we have written above.
Summary: One may not inflate a plastic or rubber air mattress or pillow on Shabbat. Nevertheless, if these objects were already inflated before the onset of Shabbat and during the course of Shabbat lost some air pressure, they may be re-inflated on Shabbat.