A broad term that applies to any change after the original purchase, such as adding equipment not a part of the original purchase. As applied to alternative fuel vehicles, it refers to conversion devices or kits for conventional fuel vehicles. Also called "aftermarket."

Addition of a pollution control device on an existing facility without making major changes to the generating plant.

A modification that can be made to an existing piece of equipment after purchase to bring it up to date.

Upgrading a fixture, room or building by installing new lighting fixtures, parts or equipment.

a replacement of a valve's main flow control trim component using the original valve body as installed without alteration

A self-ballasted replacement lamp that converts a light source to either change its characteristics or reduce energy consumption.

To replace an older component, system or refrigerant with a newer one. With respect to A/C systems, retrofit refers to replacing R12 with R134a. Changing refrigerants requires changing compressor lubricants and service fitting, and may also require other