Not lying. Most likely some relevant details are unintentionally omitted. It could be that his buddy had poor health or was too overweight. Or may be was quite stressed out even before going into that hot facility. Or stayed there longer than 10 minutes. Or the temperature was higher. Or the air was slightly toxic (that's actually my best guess). Or all of the above.

But 10 minutes exposure to 60C dry air is not nearly enough for fainting.