We investigated whether nitrogen (N₂) can be substituted for helium (He) as a carrier gas for thermal/optical carbon analysis. Eighteen filter samples of atmospheric and combustion source particles and two powder standard reference material samples (urban dust: SRM1649a and diesel exhaust particles: SRM1650b) put on filters were analyzed using both carrier gases then the peak abundances and shapes and the quantitated values were compared. For the filter samples, the total carbon (TC) concentrations and the elemental carbon (EC)/TC ratios using the N₂ carrier were >20% lower than those for the He carrier for two low concentration samples (<10 μgC) when the usual linear calibration curve was used. However, the TC concentrations using the N₂ carrier became consistent within 20% with those for the He carrier for all the filter samples when the quartic calibration curve was used. The EC/TC ratios using the N₂ carrier of 16 filter samples agreed within 20% of those for the He carrier. For the SRMs, the TC concentrations and the EC/TC ratios using the N₂ carrier agreed within 6% of those for the He carrier. Thus, the N₂-carrier measurements can provide results of the TC concentrations and the EC/TC ratios equivalent to those for the He carrier, although attention is required for low level samples.