OC-EC measurements made on PM2.5 filters collected by the York hivol sampler at the North Kensington site (London) during the ClearfLo winter IOP 2012 PM2.5 filter samples are collected with a day-night time resolution using a undenuded HiVol sampler (1.13 m3/min flow rate) owned by the University of York. Pre-baked quartz filters (QMA, 20.3x25.4 cm, Whatman) are used for collection, wrapped in aluminum foil and stored at -18 Celsius degrees until analysis. OC-EC data were taken using a Sunset OC-EC analyser owned by the University of Birmingham. OC-EC analyses were performed on 1.5 cm2 filter portions following the EUSAAR2 thermal protocol and each sample was measured at least twice Reference on OC-EC measurements and the EUSAAR2 protocol can be found in Cavalli et al., Atmos. Meas. Tech., 3 (79 to 89) 2010 The uncertainties for OC, EC and TC were 13.5%, 10.2% and 11.7% respectively. The uncertainties were estimated by using the sum of the squares of the variability of the filter samples measured in replicate within the same day No blank correction has been applied as the measured blanks were found always below the limit of detection (LoD of TC was 0.2 ug/cm2),TC was found to be at least 10 times above the LoD in all samples