We designed and evaluated the performance of a tandem technique, consisting of a previously developed versatile aerosol concentration enrichment system (VACES) combined with a compact screen-type diffusion battery that removes ambient ultrafine particles (UFP) from the airflow to enable us to conduct exposures directly on concentrated ambient accumulation mode (0.18–2.5 μm) particles. The performance of the diffusion battery was evaluated first under controlled conditions using NaCl laboratory-generated aerosols. Based on the laboratory tests, the optimum operational conditions of the diffusion battery were selected in terms of the flow rate (i.e., 5 lpm) and number of stages (i.e., 6). The diffusion battery was then deployed to our sampling site in central Los Angeles and connected to the VACES in order to evaluate the performance of the VACES/diffusion battery tandem using concentrated ambient particulate matter (PM2.5). Results of the field tests confirmed the ability of this tandem technique to concentrate effectively the accumulation mode PM with the majority of the ultrafine particles removed from the concentrated aerosol. The 50% cutpoint of the diffusion battery was at around 100 nm, while the removal efficiency exceeded 70–90% for particles smaller than 50 nm. Comparison of the mass concentrations and chemical composition of the accumulation mode PM collected using the tandem technique with those collected using a MOUDI sampler operating in parallel showed excellent overall agreement (within 5–15% variation), corroborating the effectiveness of the VACES/diffusion battery tandem technique for application in exposure studies to concentrated ambient accumulation mode PM.