Virginia Administrative Code
Title 9 - ENVIRONMENT
Agency 5 - STATE AIR POLLUTION CONTROL BOARD
Chapter 91 - REGULATIONS FOR THE CONTROL OF MOTOR VEHICLE EMISSIONS IN THE NORTHERN VIRGINIA AREA
Part X - Analyzer System Certification and Specifications for Enhanced Emissions Inspection Programs
Section 9VAC5-91-700 - Calibration of exhaust gas analyzers

1. The calibration gases for standardizing instruments shall conform to the provisions outlined in EPA420-B-04-011.

2. Gas analyzers shall pass a two-point gas calibration for HC, CO, CO2 and NO, within 72 hours before each test.

3. Gas analyzers shall pass a five-point gas audit for HC, CO, CO2, and NO at least two times within 12 months, and each time an analyzer system emissions measurement system, sensor, or other electronic components are repaired or replaced in response to an audit failure.

4. The director may reduce the frequency of calibrations in subdivision 2 of this section and audits in subdivision 3 of this section or both if evidence indicates accuracy would not be adversely affected.