The present invention is a process for transitioning from a first polymerization reaction to a second polymerization reaction incompatible with the first polymerization reaction in a gas-phase reactor. The injection port guide may be formed in plate-shape. The optical feedback loop controls power to the light source during normal operations. The wireless communication link may include an infrared link, a radio link, an acoustic link, or an inductive link. Accordingly, the door can be operated in a traditional manner while providing impact and damage protection to the door.