@st348’s answer is only partially correct. At order=1 there is no interaction between shocks and the IRFs are generated by considering only one shock at a time. Thus, for each displayed IRF, all other shocks are set to 0. If you dislike the IRFs to other shocks being displayed, consult the manual on irf_shocks
Things are more complicated at order>1 as there are now interactions between shocks. Dynare provides Generalized Impulse Response Functions (GIRFs) in this case where other shocks averaged out (see Koop/Pesaran/Potter 1996). If you have a particular type of GIRF in mind where the conditioning set involves setting all other shocks to 0, you would need to use the simult_-function to do the simulations manually.