From TV.com's episode guide: "When Hal sprays himself in the face with the fire extinguisher, it really is something that could harm him. Fire extinguishers, depending on the type, use a variety of hyper cooling foams. If sprayed in the eyes, both the fluid and the cooling effect can be very damaging. In some cases, blindness results from fractured corneas. Usually though, the eyes require a few weeks time with no usage (hence the bandaging) to recover from the nitrogen burns."
