[ham888]

Bertiebobbins is discussing how to heat if the electric is out for some time, so anything heated by electricty (no gas rememeber) will be useless once it has cooled. Chemical methods such as those activatable hand warmers may work, but not in the cage as if chewed they'd be disasterous. Also what about portable Calor gas heaters? I'd worry about the emissions from those near small furballs but one could warm a room, turn it off and move the cages in, and swap as needed.

A towel over the cage will restrict airflow and may be ingested.

Of course you can't preduct when the electricity will fail so it is likely to go off and find you unprepared. No energy = no heat.

Candles? They are a heat source, though not very much and also a fire risk... I'm trying to think what we'd do - we have a gas fire so at least we could warm one room - other than that I'd find a hotel and sneak the cages in!