IMO, alcohol is among the most volatile substances you'll ever set fire to. I don't consider alcohol stoves safe at all.

That being said, I'm a pyromaniac and will happily set fire to most substances and stoves. Given ample ventilation and meticuously attention to procedures I have no worries about doing that inside a tent or vehicle either. But I will only do that with a stove I'm intimately familiar with.

Sorry if this sounds harsh, and it is certainly not targeted at any individuals in this forum, but I think alcohol stoves are misjudged as "safe" because they are so easy and simple to use. With most other stoves you have to pay attention to procedures to get them working. With alcohol stoves, it is so easy the most obvious hazards are easily ignored. Filling an almost, but not quite empty and still burning (invisible flame) stove with liquid alcohol is my favourite example...


Personally, I'll never rely on alcohol stoves in subzero weather - too slow and too feeble heat effect. That doesn't mean they don't work - they do, I'm just not happy with what they do and the ratio of meals produced per weight or volume unit of fuel.