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<p>Oxidation flow reactors (OFRs) are frequently used to study the formation and evolution of secondary aerosol (SA) in the atmosphere and have become valuable tools for improving the accuracy of model simulations and for depicting and accelerating realistic atmospheric chemistry. Driven by rapid development of OFR techniques and the increasing appreciation of their wide application, we designed a new all-Teflon reactor, the Particle Formation Accelerator (PFA) OFR, and characterized it in the laboratory and with ambient air. A series of simulations and experiments were performed to characterize (1) flow profiles in the reactor using computational fluid dynamics (CFD) simulations, (2) the UV intensity distribution in the reactor and the influence of it and varying O<span class="inline-formula">₃</span> concentration and relative humidity (RH) on the resulting equivalent OH exposure (OH<span class="inline-formula">_exp</span>), (3) transmission efficiencies for gases and particles, (4) residence time distributions (RTDs) for gases and particles using both computational simulations and experimental verification, (5) the production yield of secondary organic aerosol (SOA) from oxidation of <span class="inline-formula"><i>α</i></span>-pinene and <span class="inline-formula"><i>m</i></span>-xylene, (6) the effect of seed particles on resulting SA concentration, and (7) SA production from ambient air in Riverside, CA, US. The reactor response and characteristics are compared with those of a smog chamber (Caltech) and of other oxidation flow reactors: the Toronto Photo-Oxidation Tube (TPOT), the Caltech Photooxidation Flow Tube (CPOT), the TUT Secondary Aerosol Reactor (TSAR), quartz and aluminum versions of Potential Aerosol Mass reactors (PAMs), and the Environment and Climate Change Canada OFR (ECCC-OFR).</p> <p>Our studies show that (1) OH<span class="inline-formula">_exp</span> can be varied over a range comparable to that of other OFRs; (2) particle transmission efficiency is over 75 % in the size range from 50 to 200 nm, after minimizing static charge on the Teflon surfaces; (3) the penetration efficiencies of CO<span class="inline-formula">₂</span> and SO<span class="inline-formula">₂</span> are 0.90 <span class="inline-formula">±</span> 0.02 and 0.76 <span class="inline-formula">±</span> 0.04, respectively, the latter of which is comparable to estimates for LVOCs; (4) a near-laminar flow profile is expected based on CFD simulations and suggested by the RTD experiment results; (5) <span class="inline-formula"><i>m</i></span>-xylene SOA and <span class="inline-formula"><i>α</i></span>-pinene SOA yields were 0.22 and 0.37, respectively, at about 3 <span class="inline-formula">×</span> 10<span class="inline-formula">¹¹</span> molec. cm<span class="inline-formula">⁻³</span> s OH exposure; (6) the mass ratio of seed particles to precursor gas has a significant effect on the amount of SOA formed; and (7) during measurements of SA production when sampling ambient air in Riverside, the mass concentration of SA formed in the reactor was an average of 1.8 times that of the ambient aerosol at the same time.</p>