RATIONALE: Helium (He) is used in cutting-edge research in industry and science as a carrier and/or ionization gas. The global He shortages have dramatically increased its prices and reduced its availability, to what comes together the current energy crisis. A strategy is proposed to save He and energy in elemental analysis/isotope ratio mass spectrometry (EA/IRMS). METHODS: A method for analysis of carbon and nitrogen isotope composition (δ¹³C and δ¹⁵N values) is proposed using two or three sequential combustion reactions in a single EA/IRMS acquisition. The methods (hereafter called 2×EA/IRMS and 3×EA/IRMS) use the time needed for the peak center and reference gas (CO₂ or N₂) pulses to measure δ¹³C or δ¹⁵N in two or three capsules with samples or standards. The combustion cycles can be replicate analyses of the same or different material. RESULTS: The methods were validated with replicate analysis of C and N in RMs and laboratory standards of a broad range of biological and geological matrices, δ¹³C and δ¹⁵N values, and C/N molar ratios. The accuracy and precision of the 2×EA/IRMS and 3×EA/IRMS values were15 essentially the same, with good agreement between the mean ± 1 SD values from RMs and standard analyses and the recommended or accepted values and their uncertainties. CONCLUSIONS: The proposed methods save He, save energy, save reference gases (CO₂, N₂), and O₂, while reducing the analysis and instrumental times by ca. 50 %.