Carbon Capture and Storage (CCS) projects, either in existing oil and gas fields to directly reduce CO2 emission, or used for pressure support and CO2 flooding, needs to be monitored to ensure that injected CO2 stays in the underground. By addition of unique RESMAN’s CCS-compatible tracers, direct proof of any leak from injectors are given from samples taken at observation points or in adjacent wells, if the storage site is located close to producing reservoirs. Using RESMAN methodology, an extreme detectability for CCS-tracers is standard. Therefore, a small tracer amount is sufficient to monitor large scale subsurface flow patterns, and storage seal is proven as long as tracers are not detected. If tracers are detected the source can be identified and leaks remediated. Tracer data are also cost-effective and can be integrated efficiently with data from other monitoring technologies, such as 4-D seismic.