Perhaps the noxious gas problem could be avoided by putting the heat pack under one side of the enclosure instead of inside it? With a rolled up towel maybe on the other end to try to level it. Or even elevating the enclosure over but not touching the heat pack to avoid too much temperature spike? I would only consider doing this in an emergency and only for short term, maybe an hour or two in the middle of the night at the coldest point to keep his body temperature from dropping too low. Barring the heat pack, you could try placing a couple pillar candles near the enclosure for a little while as long as you could watch the thermometer readings. I haven't encountered that sort of problem here, but I wouldn't worry overmuch about brief stints in less-than-ideal conditions, as long as we're not talking freezing or boiling. I'm sure whatever water you're drinking over the next few days will suffice for your BP as well.