In this conference paper the results from the first in situ quantification of HO2 from dimethyl ether oxidation (DME) at the exit of a laminar flow reactor at atmospheric pressure published in (Brumfield 2013) are reviewed. A Q-branch spectral feature at around 1396.90 cm-1 in the v2 bending fundamental was measured using Faraday rotation spectroscopy, a radical selective magneto-optical laser-based method that strongly suppresses unwanted absorption signals from non-radical species (i.e. H2O). HO2 species concentrations were obtained through non-linear fitting of the experimental spectra using an FRS spectral model and molecular parameters from the HITRAN spectral database. The HO2 species concentration was measured at various flow reactor temperatures, and the experimental HO2 concentration versus temperature profile was compared to one obtained using chemical kinetic modeling of dimethyl ether oxidation. Poor agreement between the experimental and the chemical kinetic modeling results were observed that should be attributed to possible deficiencies of the chemical kinetic model. A path flux analysis for the formation of HO2 in the DME oxidation chemical kinetic model indicates that discrepancies above 650 K arise due to uncertainties or missing reaction pathways for the formation of HCO and its subsequent reaction with O2.