EN 16976 and CEN/TS 17434 pertain to the measurement of ultrafine particles (UFP) in the atmosphere. Their goal is to harmonize (i.e. make consistent) the measurement techniques used for measuring the particle number concentration (EN 16976) and particle size distribution (CEN/TS 17434:2020). Such ‘harmonization’ ensures that data from various sites can more easily be compared. Instrument performance issues, of course, erode data quality, and undermine the extent to which data can be compared. How can the accurate performance of these continuous-use instruments be confirmed?
The authors of the CEN specifications understand the importance of periodically validating, and occasionally calibrating, the Condensation Particle Counters (CPCs) and Mobility Particle Size Spectrometer (MPSS, i.e. SMPS™) systems used in CEN-compliant ambient air monitoring efforts.
Validation: Periodic Performance Check
The EN 16976 and CEN/TS 17434:2020 specifications require that certain performance confirmation (i.e. ‘validation’) steps be taken at designated frequencies. TSI can support you in your efforts to validate your CEN-related instrumentation. These validation actions, their designated frequency, and the TSI instrumentation relevant to each step are as follows:
| Component | Action | Section CEN/TS 16976 | Section CEN/TS 17434 | Frequency | Recommended TSI® Tools |
|---|---|---|---|---|---|
| Sampling System | Confirm inlet flow | 7.6 | 8.6 | Monthly | Flow Calibrator 4148 |
| Leak check of dries | 9.2.13 | 10.2.12 | Condensation Particle Counter 3750-CEN | ||
| Condensation Particle Counter (CPC) | Inlet flow check | 9.2.7 | 10.3.3 | Flow Calibrator 4148 | |
| Zero (background) check | 9.2.5 | 10.3.7 | Particle Zero Check Filter | ||
| Scanning Mobility Particle Sizer™ (SMPS™) | Inlet flow check | n/a | 10.3.2 | Flow Calibrator 4148 | |
| Zero (background) check | 7.2.5 | Particle Zero Check Filter | |||
| Leak check | 10.3.8 | Flow Calibrator 4148 and Particle Zero Check Filter | |||
| Particle size accuracy check | 7.2.3 | Quarterly | Monodisperse Aerosol Generator 3940A | ||
| Delay time check | 10.3.6 | Monitoring license for Aerosol Instrument Manager® 11 software for SMPS™ |
Calibration: More Thorough; any Problems are Rectified
Annual calibration is required by both CEN standards; this necessitates sending the instruments in question to a calibration center such as are overseen by the European Center for Aerosol Calibration (ECAC).
During a formal calibration, the performance of the instrument is examined in greater detail than can be done in the field. In some cases, if an adjustment to the instrument is found to be necessary, the calibration center may be able to perform the adjustment. After all tests are passed, the result is an instrument that produces accurate data, and is thus ready for re-deployment for continuous monitoring in compliance with the CEN specification(s).