PM2.5 samples were collected at two sites - the Indian Institute of Technology Delhi (IITD) and Indira Gandhi Delhi Technical University for Women (IGDTUW), during the winter (Jan-Feb), pre-monsoon (May-June) and post-monsoon (Oct-Nov) in 2018 as part of the ASAP-Delhi project. Daytime (0900-2100 hour, local time) and night-time (2100-0900 hour, local time) PM2.5 samples were collected using an Enviro-sense Digitel high-volume air (500 L/min) sampler on pre-baked quartz filters (150mm diameter, Whatman QM-A), and later filters were analysed for OC/EC, ion species and metals.