Carbon cycle studies rely on the accuracy of models to estimate the amount of CO₂ being taken up by vegetation. The gas carbonyl sulfide (COS) can serve as a tool to estimate the vegetative CO₂ uptake by scaling the ecosystem uptake of COS to that of CO₂. Here we investigate the nighttime fluxes of COS. The relationships found in this study will aid in implementing nighttime COS uptake in models, which is key to obtain accurate estimates of vegetative CO₂ uptake with the use of COS.