I remember one time as I was reading, that you could not use the ventless fireplaces for more than 12 hours in a 24 hour span. What good would it do if you have a power outage that lasts for seven days? ( I remember the last ice storm we had....lucky us, we were not affected but for my relatives elsewhere in different part of town, suffered three days up to seven days without power and it was miserable that they had to go out and buy propane heaters).