Never tried the chemical type as I always felt they were too expensive per use factor.

I have (2) Jon-E's (The copies are not as well built as genuine Jon-E's.) catalytic heaters, one the small size, and one the large size. They stink until they get up to speed, and you do have to worry about not smothering them, but they work very well for my primary use which is for my hands.

For my feet, I prefer battery operated socks as I can control when and how much to heat by switching the batteries on and off. I prefer the belt mount battery holder over the sock mounted battery holder style.

For my head, nothing works as well for me as a good wool watch hat supplemented by a tunnel hood for more extreme temperatures. The biggest problem I have is a rather large head (My friends say it is my ego trying to get out, but they are just jealous.) and I have yet to find a good wool watch cap that I can wear for long peionds of time without my head feeling like a lemon being squeezed.

Once safely out ot the elements, nothing like a Jim Beam Bourbon & sour or a couple shots of good Cognac to warm up everything.

Bountyhunter