I like my Thermacell also, BUT last weekend my wife and I went camping in the high country, set up camp at 10,300' and the thermacell did not work, wouldn't lite. I contacted thermacell and they said, yip, won't work at that high altitude. We got ate up by skeeters and flys. My thermacell will work here at my house, elevation is about 6300', so some where between 6300' and 10,000', there becomes a shortage of enough oxygen for it to operate.