One of the worst side effects of playing paintball in the rain (or after the rain) is that your lens is much more likely to fog. This is because the humidity outside is extremely high and more likely to result in heavy condensation (fog).
Using a paintball mask with a dual-pane thermal lens will virtually eliminate any chance of your lens fogging in 99% of situations, but there’s always that 1% chance that your lens can still fog when playing in the rain (or after).
A dual-pane lens is simply two lenses that are separated by a small layer of foam around the outside of the lens. This small layer of space between the two lenses helps prevent lens fog by creating a buffer zone where the temperature between the two panes isn’t as contrasting as it inside or outside of the two separate lenses.