The ability to predict feature profile evolution across wafers during processing using equipment scale operating conditions is one important goal of process engineers. We present an integrated approach for simulating the multiple length scales needed to address this problem for thermal chemical vapour deposition (CVD) processes. In this approach, continuum models on the reactor scale and mesoscopic scales are coupled tightly with ballistic transport models on the feature scale to predict micro and macro loading effects in a transient environment. As an example of this approach, the transient simulation results for thermal deposition of silicon dioxide from tetraethoxysilane (TEOS) are presented. The efficiency of the approach presented and extensions to more complex systems are briefly discussed.