[Code of Federal Regulations]
[Title 40, Volume 18]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR92.122]

[Page 455]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 92--CONTROL OF AIR POLLUTION FROM LOCOMOTIVES AND LOCOMOTIVE ENGINES--
Table of Contents
 
                       Subpart B--Test Procedures
 
Sec. 92.122  Smoke meter calibration.

    The smokemeter shall be checked according to the following procedure 
prior to each test:
    (a) The zero control shall be adjusted under conditions of ``no 
smoke'' to give a recorder or data collection equipment response of 
zero;
    (b) Calibrated neutral density filters having approximately 10, 20, 
and 40 percent opacity shall be employed to check the linearity of the 
instrument. The filter(s) shall be inserted in the light path 
perpendicular to the axis of the beam and adjacent to the opening from 
which the beam of light from the light source emanates, and the recorder 
response shall be noted. Filters with exposed filtering media should be 
checked for opacity every six months; all other filters shall be checked 
every year, using NIST or equivalent reference filters. Deviations in 
excess of 1 percent of the nominal opacity shall be corrected.