My next DIY job is to sort out once and for all the glasses misting up issues I have. I have one of these gas mask face masks:
I found out that the lenses can be shot out too easily so I have used epoxy glue to reinforce around the inside.
There is a small fan inside the filter running off 2x AA batteries, I found it unreliable and when it works its okay but a little more airflow would be better. I have now cut out all the plastic internal structure of the filter and fitted an old 12V CPU cooling fan. Now all I need to do is build a power supply to fit in my shirt pocket or maybe attached to my chest rig.
If this doesn't work, then I will just need: A big backpack, portable air dehumidifier, an old air con unit......