Protonated formaldehyde (H₂COH⁺) was identified in a 1996 paper by Ohishi et al.. They found up to six lines in sources including the star-forming regions Sgr B2(M), Orion-KL, and W51 and tentative detections in NGC 7538 and DR21(OH) using the Nobeyama Radio Observatory and facilities at Kitt Peak. Confirmation of the detection includes 2008 papers by Requena-Torres et al. and Jones et al.. The detection was based upon a laboratory spectrum by Chomiak et al. Later papers by Dore and co-workers provide additional spectroscopic data for protonated formaldehyde as well as two of its isotopomers.