Code of Colorado Regulations
1000 - Department of Public Health and Environment
1001 - Air Quality Control Commission
5 CCR 1001-13 - REGULATION NUMBER 11 MOTOR VEHICLE EMISSIONS INSPECTION PROGRAM
Part C - Inspection Procedures and Requirements for Exhaust Emissions, Fuel Evaporation Control, Visible Smoke Emissions, Emissions Control Systems, On-Board Diagnostics (OBD); and Practices to Ensure Proper Emissions Related Adjustments and Repairs
Section V - EVAPORATIVE FUEL CONTROL INSPECTION PROCEDURES

Model year 1975 and newer vehicles shall be inspected for the presence and integrity of the gasoline cap(s). The gasoline cap(s) of such vehicles inspected in the nine county Front Range enhanced program area as defined in Section 42-4-304(9)(a)., shall also be inspected for sealing integrity as specified in Part F, Section IV of this regulation.

Vehicles with a missing gasoline cap(s) shall not qualify for issuance of a Certificate of Emissions Control. Motorists whose vehicles have gasoline cap(s) demonstrating excessive leakage shall be notified of the deficiency, repair/replacement and a full retest shall be mandatory.