Abstract Determining the atmospheric abundance and the emission sources of carbonyl sulfide (OCS) plays a crucial role for the sulfur budget in the atmosphere. In addition to its main anthropogenic and biogenic sources, biomass burning is assumed to be an essential, but not well constrained source of OCS. From November 2019 onward extensive bushfires along the eastern coast of Australia released huge amounts of trace species into the atmosphere; during one flight of the SouthTRAC campaign air masses were observed carrying signatures of these fires along the southern coast of South America. An analysis of the composition of air masses inside and outside the plume revealed distinct differences in the trace species abundances. Specifically, our results indicate that OCS shows no enhancement in its atmospheric mixing ratio due to the Australian fires and thus highlights the varying emission strength of OCS for different types of biomass burning.