Prompted by these EU requirements, CEN/TC 264 Air Quality established working group CEN/TC 264/WG 15 to present a manual standard gravimetric measurement method for the determination of the PM2,5 mass concentration of suspended particulate matter in ambient air.
There are no traceable reference standards for PM2,.5 measurements. Therefore, the standard measurement method set out in EN 14907  effectively defines the measured quantity by convention, specifically by the sampling inlet design and associated operational parameters covering the whole measurement process.
To support the drafting of the standard measuring method EN 14907, working group CEN/TC 264/WG 15 on PM2,5 carried out a field evaluation program at various test locations throughout the EU. Following a pilot study, 8 test locations representative of various ambient air situations were chosen so that the impact of semi volatile particulate matter to the PM2,5 mass concentration would be investigated.
The field evaluation was focused on the following aspects:
• to select, validate and assess the practicability of the designated manual gravimetric PM2,5 standard measurement method
• to determine the performance characteristics of the standard measurement method, notably measurement uncertainty
• to develop a practical test procedure to demonstrate whether non standard measurement methods (like other manual gravimetric or automatic monitoring methods) are equivalent to the designated standard method.
• to provide information on the performance and measurement uncertainties of some commonly deployed automatic PM2,5 measurement methods, in line with the uncertainty requirements set out in the data quality objectives within the Directive 1999/30/EC.
1 Measurement methods
WG 15 agreed that the candidate reference samplers to take part in the Field Test shall comprise:
(1) the 'Mini-WRAC', at the request of the EC;
(2) a Low Volume 'unconditioned' system (with no mechanism to reduce solar heating effects on the sampling line or filter), for comparability with the PM10 standard EN 12341 ;
(3) a High Volume system, for comparability with the PM10 standard EN 12341;
(4) a Low Volume 'conditioned' system, with an air flow mechanism designed to reduce solar heating effects, because of the recent understanding of the significance of these effects;
(5) a US-EPA approved WINS system, for comparability with US-EPA;
(6) a Sharp Cut Cyclone (SCC) system, because of the potential practical advantages of a cyclone inlet over an impactor inlet, provided that the SCC inlet is not commercially restricted.