### Question
How is the "mercury vapor lamp" defined?


### Answer
The term **mercury vapor lamp** is defined in *42 U.S.C. § 6291* as follows -

> a high intensity discharge lamp in which the major portion of the light is produced by radiation from mercury typically operating at a partial vapor pressure in excess of 100,000 Pa (approximately 1 atm)

#### Citation:
  - *42 U.S.C. § 6291*
  - Heading: **CHAPTER 77-ENERGY CONSERVATION > SUBCHAPTER III-IMPROVING ENERGY EFFICIENCY > Part A-Energy Conservation Program for Consumer Products Other Than Automobiles**

