Division Regarding the measurement method:

The mandate given by the Commission to CEN specified that the measurement method to be standardised is based on the gravimetric determination of the PM_2.5 mass fraction of particulate matter collected on a filter under ambient conditions. Other methods, such as the beta ray attenuation method and the tapered element oscillating microbalance (TEOM), are currently tested for equivalence with the gravimetric method by CEN WG15.