Launched in August 2025, Sentinel-5 provides daily CH₄ and CO retrievals and is sensitive to CO₂. Its shortwave-infrared (SWIR) mercury-cadmium-telluride (MCT) detectors exhibit persistence effects causing scene-dependent biases. This study quantifies these biases for CH₄, CO, CO₂, and the CH₄/CO₂ proxy using RemoTeC over regions with high radiance variability. Typical biases are small (<0.34 %), but outliers reach 1.59–4.01 %. Targeted post-filtering can reduce outliers and meet mission performance.