Portable Gas Heaters

padre wrote:
We have a trip planned for early September, 2020, inside the Rocky Mountain National Park which is at an altitude of over 8000 feet. I have been considering a portable propane heater to supplement the furnace (to save battery) but note that there are alerts about them not working above certain altitudes. For example the Mr. Buddy or Big Buddy. Do any of you have experience using such heaters at high altitudes? I will appreciate your comments. I know we will need heat and wish to conserve the batteries as much as possible

I am quoting myself the OP in order to report. We did make the trip as planned. We took a catalytic heater Wave 6 which we already had for in-home use. It worked fine and was enough, though I will have to say we were having unusually warm weather UNTIL ... the September snow storm hit. We solved that problem by "getting out of Dodge!" We left RMNP 2 days early and scooted down to Colorado Springs where we did, indeed, have snow. We were probably being extra cautious but we did not want to get stranded in a high altitude campground without any hookups or access to propane. We had a wonderful trip and thanks to all who responded to my request for advice.