[en] This report provides the results obtained for the first five tanks sampled with the Retained Gas Sampler (RGS): Tanks 241-AW-101, A-101, AN-105, AN-104, and AN-103. The RGS is a modified version of the core sampler used at Hanford. It is designed specifically, in concert with the gas extraction equipment in the hot cell, to capture and extrude a gas-containing waste sample in a hermetically sealed system. The retained gases are then extracted and stored in small gas canisters. The composition of the gases contained in the canisters was measured by mass spectroscopy. The total gas volume was obtained from analysis of the extraction process, as discussed in detail throughout this report. The following are the findings of this research: (1) The RGS is a viable approach for measuring retained gases in double- and single-shell waste tanks at Hanford. (2) Local measurements of void fraction with the RGS agree with the results obtained with the void fraction instrument (VFI) in most cases. (3) In the tanks sampled, more than 16% of the retained gas in the nonconvective layer was nitrogen (N₂). The fraction of nitrogen gas was approximately 60% in Tank 241-AW-101. This finding shows that not all the retained gas mixtures are flammable. (4) In the tanks sampled, the ratios of hydrogen to oxidizers were observed to be significantly higher than 1; i.e., these tanks are fuel-rich. Based on these observations, the RGS will be used to sample for retained gases in several single-shell tanks at Hanford. The remaining sections of this summary describe the RGS-findings for the first five tanks tested. The results are described in the order in which the tanks were sampled, to reflect the increasing experience on which RGS methods were based