Air Quality Monitoring Unit, Environment and Engineering Department
Document: Standard Operating Procedures Manual / Title: ML9841B Nitrogen Oxides AnalyserSection: 1.1.2 / Page 1 of 5
Issue Date: 15/04/03 / Revision Date: 21/2/11
Issued By: AnneMarie McCartan / Approved By: Martin Fitzpatrick
- Purpose
To ensure optimum NO2/NO/Nox data quality and capture by establishing a standard operating procedure for operating, calibrating and downloading data to comply with Council Directive 1999/30/EC.
- Scope
All existing and future ML9841B NO2/NO/Nox Nitrogen Oxides Analysers located in Multipollutant sites under the control of the Air Quality Monitoring Unit.
- Responsibility
PEHO or designate
- Records/Related Documents
EU Directive 1999/30/EC related to limit values for SO2, NO2 and oxides of nitrogen, particulate and lead in ambient air.
ML9841B Nitrogen Oxides Analyser Instruction Manual
Appendix I:Gas Cylinder Listings & Advisory Sheet
Appendix V: Guidance document for downloading data using Enview software.
Multi-pollutant Site Visit Record.
NOx ML9841B Internal Calibration Record
External Calibration & Maintenance record sheet
Electronic Records (L:\Air Monitoring with relevant folders for all raw data).
Log of Multipollutant Site Downloads
Appendix III: Editing Nox/SO2/CO data
Equipment Maintenance & Repair Log
- Procedure
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No.Activity
- Introduction
Nitrogen Dioxide (NO2) is one of a number of important oxides of nitrogen present in the atmosphere. Nitric Oxide (NO) and Nitrogen Dioxide (NO2) (together termed NOx) are the most abundant man-made oxides of nitrogen in urban areas; these are formed in all high temperature combustion processes although nitric oxide predominates. Nitric Oxide is not generally considered to be harmful to health at concentrations found in the ambient atmosphere.
Nitrogen Dioxide is formed by the oxidisation of nitric oxide by ozone and oxygen, and is the particular oxide of nitrogen that is considered to be a major pollutant.
The production of meaningful data from the multipollutant site necessitates the calibration of the M9841B Nitrogen Oxides analyser using traceable standards.
Document: Standard Operating Procedures Manual / Title: ML9841B Nitrogen Oxides AnalyserSection: 1.1.2 / Page 2 of 5
Issue Date: 15/04/03 / Revision Date: 21/2/11
Issued By: AnneMarie McCartan / Approved By: Martin Fitzpatrick
- Equipment
M9841B Nitrogen Oxides Analyser
Code activated switch (if applicable)
Data Logger (if applicable)
Modem (if applicable)
Calibration Gases (Ref. S.3.1)
2.1) Equipment Checks
The officer carries out checks to ensure that all equipment is working correctly or takes corrective action should some equipment be found to be inoperable or faulty. If equipment is found to be inoperable or faulty, record on the Multi-Pollutant Site Visit Record and inform the officer with responsibility for that equipment.
2.1.2) ML9841B Nitrogen Oxides Analyser
Instrument faults will be reported on the status line which appears one line below the instrument status display. The following rules apply governing the information displayed on this line: If there are no failures, the status line is blank. If there is a single failure, that failure is displayed on the status line i.e. zero flow, heater fault etc. The status line will clear when the fault clears. If there are multiple failures, the failure at the top of the failure list will be displayed on the status line. When this failure clears, the next failure on the list will be displayed. The entire list of failures is displayed on the SYSTEM FAULTS screen.
Faults must be recorded on the NOx ML9841B Internal calibration record if noted during calibration and on the multi-pollutant site visit record. Note specific error conditions in event log if fault has occurred.
NOTE: ALL FAULTS REQUIRING CONTACT WITH THE EQUIPMENT PROVIDERS MUST BE RECORDED ON THE EQUIPMENT MAINTENANCE & REPAIR LOG
2.1.3)Calibration Gas Bottles
The officer must ensure that all calibration gases that are brought in from suppliers comply with the requirements as defined by the instrument.
All litre bottles should be turned on as required during the calibration with their regulators set appropriately.
Refer to Cylinder Listing & Advisory Sheet for guidance with respect to cylinder management contained Appendix I of in the Standard Operating Procedures Manual.
Document: Standard Operating Procedures Manual / Title: ML9841B Nitrogen Oxides AnalyserSection: 1.1.2 / Page 3 of 5
Issue Date: 15/04/03 / Revision Date: 21/2/11
Issued By: AnneMarie McCartan / Approved By: Martin Fitzpatrick
- Calibration
3.1 Frequency
The officer ensures that the analyser is calibrated at the frequency scheduled below.
To ensure optimum data quality and capture, a two-tier system of calibration and analyser test procedures will be employed. The major components of this system are briefly described below:
a) Monthly manual calibrations
These will be performed by the officer every month except during months when an external calibration is carried out. Instrument drifts will be fully quantified by calibrating analysers monthly with documented and traceable calibration standards. Ref. 3.3. If there is a drift of >15% from the last calibration, repeat calibration until reading comes back to within 15%. The percentage drift from the previous month shall be recorded on the Internal Calibration Record.
b) External calibrations
These exercises, performed by external contractors in conjunction with both the six monthly instrument service and any additional maintenance work, will ensure that measurements from any station are completely representative and intercomparable. The calibration will also act as an independent audit of the system performance at each monitoring site. In this way, any site-specific problems that may have developed and remained undetected, will then be fully quantified. The external service contractor must complete the External Service and Calibration Record detailing the extent of the work carried out, if any, together with the pre and post service calibration levels.
3.2Filter Changing
The analyser sample inlet filters require changing on a fortnightly basis approximately at all sites. Change filter after the span check but before the calibration is carried out. Record filter change on multi-pollutant site visit record or on internal calibration record if filter is changed at time of calibration. In the event of a filter paper appearing badly soiled, the site operator should make a specific note on the checklist.
Use PTFE Membrane Filters (P/N 98000098-1M) supplied by EMS.
Document: Standard Operating Procedures Manual / Title: ML9841B Nitrogen Oxides AnalyserSection: 1.1.2 / Page 4 of 5
Issue Date: 15/04/03 / Revision Date: 21/2/11
Issued By: AnneMarie McCartan / Approved By: Martin Fitzpatrick
3.3 Calibration Procedures
Note: During calibration procedures “Stability” is defined as a variation of less than 0.1ppb over a one minute period for the analyser.
Zero and span calibration checks are used to provide a two-point calibration or an indication of analyser stability and function.
Zero Calibration Check
3.3.1Attach the zero air cylinder to the analyser.Set zero gas flow so that a small excess passes to atmosphere on the open end of the tee-piece. Allow the analyser to sample zero air for up to 15 minutes, or until the NO2/NO/NOx readings drift by no more than 1% of their full scale ranges during a 15 minute period.
3.3.2Record the final three stable zero air responses to generate an average on the NOx ML9841B Internal Calibration Record. Turn off zero air and detach cylinder tubing from analyser.
Span Calibration Check
3.3.3Attach calibration gas cylinder to the sample inlet point. Set calibration gas flow so that a small excess passes to atmosphere on the open end of the tee-piece.
3.3.4Allow the analyser to sample calibration gas until a stable NOx/NO/NO2 response is obtained. This normally takes approximately 15 minutes but the operator must wait until a stable reading is obtained. During calibration procedures “Stability” is defined as a variation of less than 0.1 ppb over a one minute period.
3.3.5Record the final three stable NOx and NO responses to generate an average on the NOx ML9841B Internal Calibration Record.
3.3.6Change the filter.
3.3.7From the primary screen, press either the up or down arrow key until the display prompts START MANUAL CALIBRATION? YES. Confirm that the display reads yes and press enter. A backlit cursor will be displayed on the Nox concentration display.
Document: Standard Operating Procedures Manual / Title: ML9841B Nitrogen Oxides AnalyserSection: 1.1.2 / Page 5 of 5
Issue Date: 15/04/03 / Revision Date: 21/2/11
Issued By: AnneMarie McCartan / Approved By: Martin Fitzpatrick
3.3.8Use the select key to move the position of the backlit cursor, and the Up and Down arrow keys to raise or lower the value of the backlit digit until the span calibration gas concentration value is displayed. When the desired concentration is displayed press Enter.
3.3.9Press Enter on two more occasions unless converter efficiency is known to be other than 100% whereupon it should be altered.
3.3.10Turn off calibration gas and detach cylinder tubing.
3.3.11The INSTRUMENT GAIN value should be recorded for future reference on the ML9841B Internal Calibration Record. If the instrument gain value is greater than 60, carry out the above procedure again to ensure that it was performed correctly. If the same result is achieved consult with the operating manual and PEHO or contact the relevant service contractor to arrange a site visit.
3.3.12Record the cylinder pressures of the zero air and calibration gas cylinder on the Internal Calibration record after each calibration.
3.3.13Ensure that all calibration data has been entered on the ML9841B Internal Calibration Record Sheet. Sign and date record. Note calibration check on the multi-pollutant site visit record.
- Data Management/Validation
The minimum data capture required is 90%, this does not include losses of data due to the regular calibration or the normal maintenance of the instrumentation.
The officer ensures that data is downloaded on a daily basis using Enview software and stored in the relevant sub-directory located in L:\air monitoring. Record downloaded filename on the Log of Ballyfermot MPS Download record.
(Refer to Guidance document for downloading data using Enview Software contained in Appendix V of the Standard Operating Procedures Manual).
Each month’s raw data is validated by using the figures generated during internal and external calibrations. Validation is undertaken by editing the data using results generated during the Zero and Span calibration checks described in S3.3.
The validity of data must be assessed when a fault occurs which results in the analyser operating outside of its specifications (see s.2.1.3). The final decision regarding the validity and release of data lies with the PEHO.
A detailed editing and final reporting procedure is described in Appendix III: Editing Nox/SO2/CO data.