In this paper, we present a single chip nanosensor composed of Single-Walled Carbon Nanotubes (SWNTs) integrated on complementary metal oxide semiconductor (CMOS) circuitry with custom designed on-chip amplifiers for chemical agent detection. The SWNTs were integrated on CMOS circuitry utilizing a low temperature and low voltage Dielectrophoretic (DEP) assembly process. Furthermore, we incorporated different sequences of single-stranded DNA (ss-DNA) on to SWNTs which improved their response to two toxic and explosive gases, namely Dimethyl methylphosphonate (DMMP) (an analog of nerve agent sarin [1]) by 9 times and Dinitrotoluene (DNT) (a byproduct of TNT [2]) by 12 times. In addition, the change in resistance (ΔR/R) of SWNT sensors increased from 12% to 24% when the concentration of DMMP vapor was increased from 8 ppm to 72 ppm; While ΔR/R increased from 7% to 23% when the concentration of DNT was increased from 9 ppm to 46 ppm. The SWNTs coupled with ss-DNA integrated onto CMOS circuitry shows great promise for monitoring low concentrations of toxic and explosive gases and potentially can be used to realize ultra-sensitive nanosensors.