We have also calculated lower limits to the mixing time of CO2 in 200 nm SOA particles as a function of temperature (Fig. , dashed line) using Eq. 2-4. 200 nm particles were used for these calculations since they approximately correspond to the median diameter of an accumulation mode particle in the troposphere. In this case, the lower limits to the mixing times were 0.04 and 0.004 s at 36 and 52 °C, respectively. If the mixing time of CO2 is 0.04 to 0.004 s, any CO2 produced in the particles during heating would very quickly escape the particles, and boiling would not be expected. However, the mixing times could be larger than 0.04 and 0.004 s since our calculated mixing times correspond to lower limits. As a result, we are not able to rule out boiling in 200 nm catechol SOA particles during heating. Additional experiments are needed to better constrain the viscosity and mixing times of CO2 at warm temperatures to determine if boiling can occur in 200 nm catechol SOA at mild heating temperatures.