Rated lifetime for general service incandescent lamps
Rated lifetime for general service incandescent lamps means the length of operating time of a sample of lamps (as defined in 429.27(2)(iv) of this chapter) between first use and failure of 50 percent of the sample size in accordance with test procedures described in IESNA LM-49 (incorporated by reference; see 430.3), as determined in section 4.2 of Appendix R of this subpart. The operating time is based on the middle lamp operating time for an odd number of samples and the average operating time of the two middle lamps for an even number of samples.
10 CFR § 430.2
For purposes of this part, words shall be defined as provided for in section 321 of the Act and as follows -