If BBOA contain a single phase, then semivolatile organic compounds can partition into the entire aerosol mass. On the other hand, if phase separation occurs, semivolatile organic compounds may only partition into a portion of the aerosol mass, reducing the gas-to-particle partitioning of semivolatile organic compounds. Therefore, models that assume single-phase BBOA may be overestimating particle growth. Phase separation within individual particles can increase the cloud condensation nucleation activity of organic aerosols by moving the lower surface tension organics to the outside of the particle. To account for two phases in BBOA, atmospheric models could assume two phases and model SVOCs partitioning only into the more polar phase. In addition, atmospheric models could assume that the low polarity phase does not take up water, while the high polarity phase takes up water with a given hygroscopicity. If phase separation occurs within individual particles, the outer low polarity phase could form a complete or partial surface active organic monolayer, which enhances cloud condensation nucleation activation, similar to the approaches in Ovadnevaite et al. and Ruehl et al. Experiments are needed to test these speculations.