The 3M light pipe is a long, transparent, hollow cylinder with a prismatic surface developed by 3M that distributes the light uniformly over its length.[10] Light pipes can be as long as 40 metres (130 ft) and are assembled on site from shorter, modular units. The light pipe is attached to the parabolic reflector of the sulfur lamp. For shorter pipes, there will be a mirror at the opposite end; for longer ones, there will be a lamp at each end. The overall appearance of a light pipe has been compared to that of a giant-sized fluorescent tube. One sulfur lamp with a light pipe can replace dozens of HID lamps. In the National Air and Space Museum, three lamps, each with a 27-metre (89 ft) pipe, replaced 94 HID lamps while greatly increasing the amount of light delivered.[3]
The greatly reduced number of lamps may simplify maintenance and reduce installation costs but may also require a backup system for areas where lighting is critical. The light pipes allow the lamp to be placed in an easily accessible area for maintenance and away from places where the heat of the lamp may be a problem.