He might just be shielding his face from the heat. That said, I saw a little plant that almost survived the lava flow, and it was much closer than he was, so idk.
Normally when I see geologists standing around lava they have masks on, so I’d assume he has one under whatever he’s got on his face. Either that or maybe he was getting a couple quick scoops and wasn’t going to be standing around long enough for a mask to make a huge difference.