This study investigates the impact of carbon deposition on the dynamic response of fast-response Atomic Layer Thermopile (ALTP) heat-flux sensors in sooting and particle-laden environments. Sensors exposed to real operating conditions and to controlled laboratory coatings were characterized using laser-based frequency-response calibration from 1kHz to 2MHz and compared with finite-element simulations. Carbon deposits cause a pronounced reduction in sensor bandwidth and increased attenuation of high-frequency signals, while the static sensitivity remains largely unchanged and within the ±14% calibration uncertainty. Systematic variations of carbon layer thickness up to several micrometers reveal a strong dependence of the −3dB cut-off frequency on deposition thickness, from which an empirical decay function was derived. For example, the cut-off frequency decreases from approximately 200kHz for clean sensors to about 150kHz for deposited sensors under realistic conditions. A finite-element model reproduces the observed trends, confirming that increasing deposition adds thermal resistance and inertia. Deviations at larger thicknesses are partly attributed to the experimental normalization constraint, since the lowest experimentally accessible reference frequency of 1kHz, which possibly does not represent the low-frequency limit for larger thicknesses. When using the same normalization frequency, good agreement between simulation and experimental data is observed. The results demonstrate that surface deposits primarily affect the dynamic response of ALTP sensors by introducing a thickness-dependent low-pass filtering effect which can lead to an underestimation of high-frequency heat-flux fluctuations. The presented empirical relation provides a basis for correcting deposition-induced dynamic errors and improving the reliability of high-frequency heat-flux measurements.