ABSTRACTWe developed a passive sampler for time-integrated collection and radiocarbon (¹⁴C) analysis of soil respiration, a major flux in the global C cycle. It consists of a permanent access well that controls the CO₂uptake rate and an exchangeable molecular sieve CO₂trap. We tested how access well dimensions and environmental conditions affect collected CO₂, and optimized cleaning procedures to minimize¹⁴CO₂memory. We also deployed two generations of the sampler in Arctic tundra for up to two years, collecting CO₂over periods of 3 days–2 months, while monitoring soil temperature, volumetric water content, and CO₂concentration. The sampler collects CO₂at a rate proportional to the length of a silicone tubing inlet (7–26 µg CO₂-C day^-1·m Si^-1). With constant sampler dimensions in the field, CO₂recovery is best explained by soil temperature. We retrieved 0.1–5.3 mg C from the 1st and 0.6–13 mg C from the 2nd generation samplers, equivalent to uptake rates of 2–215 (n=17) and 10–247 µg CO₂-C day^-1(n=20), respectively. The method blank is 8 ± 6 µg C (mean ± sd,n=8), with a radiocarbon content (fraction modern) ranging from 0.5875–0.6013 (n=2). The sampler enables more continuous investigations of soil C emission sources and is suitable for Arctic environments.