Face masks for hi alt trekking?

(Also posted on Gear Review page but might be more appropriate here.)
Hi, there are lots of face masks out there at present. In my hi alt trekking I find a buff or balaclava doesn't sufficiently warm the breath and often the condensation is a bit much. Given the huge numbers of masks around in this Covid time I wondered if anyone has a recommendation for a mask that might work at hi-alt.
I am thinking that a mask with a valve may at least partially overcome this problem. (BTW, I am aware health authorities don't recommend them for Covid - but I am only thinking hi-alt.)
I have seen expensive masks advertised for use by outdoor workers in really cold areas. And some have copper mesh valves - the theory being the out-breath warms the mesh which then warms the in-breath. But apart from the cost there seems to doubt if they really work - and the condensation may still be a problem.
Just seems like a good opportunity to test some cheapish masks while mask wearing (here in Vic) is compulsory.
Thanks. Grahame
Hi, there are lots of face masks out there at present. In my hi alt trekking I find a buff or balaclava doesn't sufficiently warm the breath and often the condensation is a bit much. Given the huge numbers of masks around in this Covid time I wondered if anyone has a recommendation for a mask that might work at hi-alt.
I am thinking that a mask with a valve may at least partially overcome this problem. (BTW, I am aware health authorities don't recommend them for Covid - but I am only thinking hi-alt.)
I have seen expensive masks advertised for use by outdoor workers in really cold areas. And some have copper mesh valves - the theory being the out-breath warms the mesh which then warms the in-breath. But apart from the cost there seems to doubt if they really work - and the condensation may still be a problem.
Just seems like a good opportunity to test some cheapish masks while mask wearing (here in Vic) is compulsory.
Thanks. Grahame