Metrology of Aviation non-volatile Particulate Matter (nvPM): Developing a Global Black Carbon Emissions Standard for Aviation

Over the past two decades, advances in the sampling and measurement of non-volatile aerosol emissions from large aircraft engines have led to the first new regulation for the emissions certification of gas turbine engines in over forty years (Vasilatou et al., 2025). Contributions to this effort from aerosol researchers were essential, and are discussed in this high-level review.

At the engine exit plane, emissions are either non-volatile particulate matter (nvPM) or gaseous, as species that may form volatile particles downstream of the engine are in the vapour phase in the high temperature exhaust. nvPM is also known as soot or black carbon (BC). The regulations require the mass concentration and the number concentration of nvPM aerosol particles to be measured, and recently the challenge of measuring the particle size distribution is also being considered for adoption.

The challenges for the instrumentation are multiple, as these particles are smaller than emissions from many other sources (mobility diameters as small as 10 nm GMD) and concentrations often lower than 10 µg/m3. The instruments need to be highly selective to nvPM and resistant to interferences from changes in gas composition. As emissions certification of an engine can cost over $1M in net costs, there is a strong desire to minimize testing time and thus there is a requirement to provide results in real time at a 1 Hz rate.

The standard that is in use has high uncertainties (20% for both mass and number) and suffers from large losses, especially for the smallest particles. There is a need to reduce the uncertainties and to correct for the losses so that the emission rate at the engine exit plane can be determined for emissions inventories.

The development of the methodology for sampling and measurement is discussed, along with the metrological approach that was taken, and current developments and future research are touched upon.

K. Vasilatou, K. Iida, M. Kazemimanesh, J. Olfert, H. Sakurai, T.A. Sipkens, G.J. Smallwood. Aerosol physical characterization: a review on the current state of aerosol documentary standards and calibration strategies. J. Aerosol Sci., 183 (2025), Article 106483. https://doi.org/10.1016/j.jaerosci.2024.106483