The NSA CrossVentâ„¢ ArcGuardâ„¢ Arc Flash Hood provides a gentle breeze that keeps wearers cool and their faceshield clear. Small (60 mm), quiet fans are powered by standard AA batteries. Available in 20, 40, 50, 65 and 100 cal/cm2 protection levels, the hood provides the confidence of ArcGuardâ„¢ protection.National Safety Apparel, Inc., Cleveland, OH.