83 Ill. Adm. Code 535.20
Application
Section 535.20 Application
This Part establishes the procedures for completing
certificates that a public utility shall require from employees or contractors
before any work is performed by these employees or contractors on a facility
used for the distribution of natural gas and the procedures for the conducting
of mercury vapor tests and the use of mercury vapor testing equipment by the
public utility, its agents, or its contractors.