Scarlett served on several committees, including as the Chairman of the ISO Committee TC/24- “Methods of Particle Sizing other than Sieving”, Chairman of the Particle Size group of the Royal Society of Chemistry, and Secretary of the Particle Technology Subject group of the Institution of Chemical Engineers. He was a member of the AIChE Particle Technology Forum and of the Working Party on Particle Characterization and Agglomeration for the European Federation of Chemical Engineering.