With the extent of international usage and the critical role phosphine gas (PH3) plays in commercial pest control, identification of the residual components deposited during fumigation is mandatory. It has been postulated that these infrequent residues are primarily composed of phosphoric acid or reduced forms of phosphoric acid [hypophosphorous acid (H3PO2) and phosphorous acid (H3PO3)], due to the oxidative degradation of phosphine. Using environmental scanning electron microscopy, gas phase Fourier transform infrared spectroscopy, and X-ray fluorescence spectroscopy, the structural elucidation and formation mechanism of the yellow amorphous polyhydric phosphorus polymers (P(x)H(y)) that occur in addition to the lower oxyacids of phosphorus in residues deposited during PH3 fumigations of select tobacco commodities are explored. This research determined that nitric oxide gas (or nitrogen dioxide) initiates residue formation of phosphorus hydride polymers and phosphorus oxyacids during PH3 fumigations of stored products.