Imagine your home thermostat gradually starts showing a temperature that's slightly off, even though the actual room temperature hasn't changed. Signal drift in a gas sensor works in a similar way. A gas sensor’s readings can slowly become less accurate over time, even when the concentration of gas being measured does not change. The sensor’s output "drifts" away from the correct value, leading to inaccurate results. This drift can occur over weeks, months, or years, depending on the sensor and its environment. It normally happens very slowly, but the effect becomes more pronounced over time.