Nevada Division of Environmental Protection
  State of Nevada
Division of Environmental Protection
  Bureau of Air Quality Planning
  901 So. Stewart St., Suite 4001 • Carson City, NV 89701
Phone: (775) 687-9349 • FAX: (775) 687-6396
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Emissions Auditing Branch - Monitor Audits

Auditing Branch


The Auditing Branch performs two core functions:

CEMS Auditing

The Bureau of Air Quality Planning approves the location and operation of Continuous Emissions Monitoring Systems (CEMS) and reviews and evaluates the validity of the data collected so that the information can be used to demonstrate compliance with permitted emissions limits.

Ambient Monitoring Auditing

Monitoring of the quality of the ambient air is performed by the Bureau's Ambient Air Quality Monitoring Branch. To provide an independent verification of the validity of the ambient data collected, the Auditing Branch conducts independent audits of the various state-operated monitoring sites throughout the state. In addition, the Auditing Branch also reviews monitoring Quality Assurance Project Plans (QAPPs)/Protocols from facilities that conduct monitoring to support air quality permitting applications. These QAPPs ensure that the data collected by the facility will be acceptable to the Air Bureaus for the permitting process.

CEMS Audits

Some facilities are required to install Continuous Emissions Monitoring Systems (CEMS) to ensure that the source or sources monitored do not exceed the allowed permitted emissions limit. Installing and operating a CEMS is a complex and expensive undertaking. As a result of these permitting requirements, the Bureau of Air Quality Planning approves the location and operation of these monitors and reviews and evaluates the validity of the data collected to ensure, to the greatest extent possible, that the information can be used to support compliance determinations.

Emissions monitored by CEMS may include: sulfur dioxide, nitrogen oxides, carbon monoxide, carbon dioxide, hydrogen chloride, airborne particulate matter, mercury, volatile organic compounds, and oxygen. CEM systems can also measure air flow, flue gas opacity and moisture content. The owner or operator must develop and implement a written quality assurance/quality control plan for each CEMS. The quality control plan must include complete, step-by-step procedures and operations for calibration checks, calibration adjustments, preventive maintenance, audits, and record-keeping and reporting. The quality assurance plan must include procedures for conducting periodic performance tests. EPA rules specify the reference methods and standards that are used to substantiate the accuracy and precision of the CEMS.

CEMS located at power generation facilities are required to undergo period certification of the CEMS that must be performed by an independent firm. This assessment of system accuracy is called a Relative Accuracy Test Audit (RATA). A separate and independent CEMS is temporarily placed where it can collect emissions data in tandem with CEMS being audited. These periodic evaluations of the equipment, including daily calibration tests and the RATAs, must be recorded and reported to the NDEP. The Auditing Branch then reviews the results of the quality assurance checks.

Monitor Audits

Facilities that hold Class I and certain Class II permits are required to monitor ambient air quality immediately downwind of their facility and report the results to NDEP on a quarterly basis. The operation of the monitoring sites, which also include meteorological stations, must be conducted in accordance with EPA regulations and guidance and with the NDEP monitoring guidelines. The Auditing Branch reviews these reports for quality, accuracy, and compliance with the applicable monitoring guidance as needed for permitting actions. NDEP also reviews the auditing of these monitoring sites performed by independent auditors.

Plans for monitoring the background ambient air quality and meteorological conditions at newly proposed facilities are also reviewed by the Auditing Branch as part of the permit approval process. The review includes the site selection for the proposed monitor and the proposed monitoring Quality Assurance Project Plans (QAPPs). This is done to ensure that valid, consistent, and usable data will be obtained. Data are then used for pre-construction dispersion modeling and for post-construction permitting actions for facilities required to do post-construction monitoring by the conditions specified in their air quality permit.

Monitoring at State-Operated Ambient Monitoring Sites

The Auditing Branch conducts independent audits of monitoring sites operated throughout the state by the NDEP Ambient Air Quality Monitoring Branch. This provides independent verification that the collected ambient air quality data are valid.