PYROPAK® Gerbs DESCRIPTION PYROPAK® Gerbs are tube devices which produce a dense plume of sparks with little or no fallout. Each is labeled according to color and performance. Each label gives two numbers, such as 10 x 12 or 8 x 8. The first number refers to the duration, or burn time, in seconds. The second number refers to the clearance height needed, in feet, when the device is fired vertically. SAFETY A 10 x 12 Gerb, for example, burns 10 seconds with a vertical spark height of just under 12 feet (3.65 meters). Be certain there is enough clearance...