UK based environmental monitoring specialist Air Monitors has been awarded a contract by the Environment Agency to supply real-time particulate matter (PM) monitors to support the Automatic Urban and Rural Network (AURN). According to the terms of the contract, the firm will supply FIDAS 200 PM monitors for the continuous measurement of particle size for PM10, PM2.5 and as dual instruments which measure both PM10 and PM2.5 size fractions at the same time.
“This is an extremely important award,” says Jim Mills, Air Monitors Managing Director. “Not just because of the size of the award, but also because this new technology will provide greater insight into PM – one of the air quality parameters of greatest concern.”
The FIDAS 200 is certified as equivalent to the PM10 and PM2.5 reference methods both by TÜV and to Defra’s MCERTS for UK Particulate Matter Standard. In the process of achieving this certification, the FIDAS passed the field tests with the lowest expanded uncertainty for PM10 of any PM monitor approved for use in the UK by Defra and the Environment Agency. In addition to the performance advantages of this technology, Jim says: “The operating costs are also extremely low; the requirement for consumables is almost nil, no filter is necessary for example, and its power consumption is a fraction of most other monitors. In addition, calibration can be conducted quickly and easily in the field with a simple monodisperse powder test which is only required once every 3 months.”
Light work
Employing a well-established measurement technology – optical light scattering of single particles – the FIDAS 200 is equipped with a high intensity LED light source, which is extremely stable, delivering a long lifetime, with minimal service requirements. An optical aerosol spectrometer determines the particle size using Lorenz‐Mie scattered light analysis of single particles. These particles move through an optical measurement volume that is homogeneously illuminated with white light, and each particle generates a scattered light impulse that is detected at an angle of 90 degrees. The particle number measurement is based on the number of scattered light impulses, and the level of the scattered light impulse is a measure of the particle diameter. The mass concentration is then derived by a proprietary algorithm from the number and size distribution.
Designed for reliability, the FIDAS 200 operates two sample pumps in parallel, providing redundancy protection, and the instrument continuously monitors status and calibration. As a result, field installations can exhibit data capture rates exceeding 99%.
Accuracy measures
Operating with a volume flow of approx. 0.3m3/h the FIDAS 200 is equipped with a Sigma‐2 sampling head, which enables representative measurements even under strong wind conditions. The sampling system includes an intelligent air drying system (IADS) which prevents measurement inaccuracies caused by condensation from high humidity. This means that it will continue to function correctly in misty or foggy conditions but without the loss of semi-volatile fractions of the PM. In situations where users require chemical analysis of the aerosol, it is also possible to fit an inline filter which collects the PM after the optical analysis chamber.
Summarising, Mills said: “This contract could lead to a potential 70 PM monitors being ordered from us over 4 years (2 years plus two 1 year extensions). An alternative type of PM monitor will also be supplied as part of the Environment Agency contract, but in the light of the advantages delivered by the FIDAS 200 we believe that the FIDAS 200 is the instrument of choice. As soon as the contract was awarded we received orders for multiple FIDAS monitors, valued at over £300k, and we look forward to installing many more over the coming years.”
