It is not necessary to inventory every lamp installed in the project building. However in order to accurately determine which types and how many lamps should be listed in the purchasing plan, it is necessary to take inventory of at least 90% of the fixture types in the building (including hard-wired, portable, and task lighting). You will also need to inventory the number of lamps associated with each fixture type. Taking an inventory of fixtures will be less time-consuming than an inventory of every installed lamp. You can then determine appropriate low- or no-mercury lamp options for the inventoried fixtures and include them in the purchasing plan.