Q. Can one use a heat-pack or pad outside during Shabbos to keep warm when davening in a backyard minyan? Can one use battery heated socks to be used during Shabbos
.
A. Heat packs or pads can provide heat by a chemical exothermic reaction or by the heating provided by batteries connected to a wire filament. Poskim deal with issues of nolad (creating new objects or situations), hatmanah bedovor hamosif hevel as well as muktzah or being a bossis l’dovor ho’osur).
However, when opened, connected and the controls well sealed and protected before the beginning of Shabbos, many Poskim permit their use. This being similar to the electrical blanket mentioned above.
The same in principle should apply to battery heated socks, that usually last for about four hours.
Horav Shlomo Miller’s Shlit’a opinion is to permit their use only on need or when health issues are involved.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a