Fulminic acid (HCNO) was identified recently by Marcelino et al. in three pre-stellar cores (B1, L1544, L183)) and in the envelope of L1527, a low-mass protostar in Taurus using the IRAM 30m telescope.

HCNO is the second [H,N,C,O] isomer to be identified, following isocyanic acid (HNCO). A third isomer, cyanic acid (HOCN), has been tentatively observed as well. Fulminic acid is very unstable; its fulminate salts are used as explosives.