I do most of my runs outside, usually carrying a mask but only putting it on for short stretches if at all. But, most weeks there are one or two days where my best option to get a run in is to use a treadmill at the gym, where I'm required to wear a mask the whole time. (Since this is LetsRun: I'm not looking for opinions on whether gyms should require masks, whether I should ever run on the treadmill, or whether I should wear a mask to run outdoors.)
Treadmill runs start out fine, the mask is a little annoying but not too bad. Then after about 10 minutes, if I'm doing more than very easy pace, my mask starts to get soaked in sweat. At that point it becomes much less breathable, and I feel like I'm suffocating. No matter how much I slow down to try to catch my breath, once the mask gets wet the run is pretty much over. For reference, I've been using this Adidas mask:
https://www.adidas.com/us/face-covers-3-pack-m-l/H08837.html
Has anyone found a mask that isn't completely terrible to run in when it's wet? Online reviews aren't helpful. The UnderArmour masks look like they might be a little better, but I don't want to spend the $30 on one if it's just going to have the exact same issue.