The discovery of the linear molecule thiofulminic acid (HCNS) toward TMC-1 was reported in 2024 by Cernicharo and co-workers. The observations utilized the Yebes 40m and the IRAM 30m radiotelescopes. The detection was based on rotational measurements published by McGuire and co-workers in 2016; they had sought HCNS toward Sgr B2(N) without success. (The measurements and search were reported initially in 2009 by McCarthy and co-workers.) HCNS has not yet been the reported subject of further observations, but Ben Huria and co-workers have characterized its de-excitation behavior in collisions with He.

Thiofulminic acid is the sulfur analog of fulminic acid, discovered in 2009. As in the [H,C,N,O] family, there are four [H,C,N,S] species. The more stable O and S species in the family have all been previously detected: HNCO / HNCS and HOCN / HSCN.