Prior to the invention of Particulate Matter sensors, Diesel Particulate Filter (DPF) monitoring was done indirectly – utilizing ΔP (differential pressure) sensors. Bosch began developing direct diesel Particulate Matter sensors in the mid-to-late 2000’s, with official rollout beginning as far back as 2013. This timing was closely tied to the announcement of Euro 6, and EPA 13/17 emission requirements that mandated on-board monitoring of DPF via real-time soot detection. Particulate Matter sensors offer far more accurate soot measurements compared to a ΔP sensor, while also having many additional benefits over a ΔP sensor.