Visibility of strong AGN emission lines as a function of the redshift in the wavelength range of the HETDEX survey. The O VI λ1034 emission is usually highly noisy due to strong foreground absorbers, and N V λ1241 is often blended with Lyα. These two lines are thus plotted as dashed lines. The gray shaded region at 0.96 < z < 1.26 shows one representative redshift range where only one emission is visible. We note here that MgII λ2799 is the reddest emission we searched in this paper. We leave the search for emission lines of AGN at lower redshifts, such as the [NeV] λ3426 emission and the Balmer emissions, for the next data release.