Hydrogen sulfide (H 2 S) scavengers have been used extensively in different field operations such as drilling and acid stimulation treatments. Typically, H 2 S scavengers are preliminarily designed to react effectively at different in-situ conditions. For example, Triazine-based scavengers are designed for neutral-high pH conditions, while aldehyde-based scavengers are intended for low pH conditions. However, reaction products of these scavengers with H 2 S could lead to potential formation damage.The efficiency of two Triazine-based H 2 S scavengers were investigated over a wide-range of parameters: solution pH value, temperature and exposure time. Additionally, the effects of both scavenger concentration and its ratio to H 2 S gas on the scavenging capacity were explored. In this work, the scavenger concentration varied from 1 to 5 vol%, reaction temperatures up to 50°C.Earlier studies have shown that, at low pH, triazine-based have a very low efficiency in scavenging H 2 S because the hydrolysis rate of triazine is faster than the reaction rate with H 2 S. Nonetheless, in this study, it was found that long exposure time between triazine-based scavengers and H 2 S can result in significant scavenging efficiency even at low pH values. Doubling the exposure time had almost doubled the amount of scavenged H 2 S in acidic solutions. In addition, this work, for the first time, highlights the possibility of calcium sulfide (CaS) precipitation in spent acid containing H 2 S scavengers. This precipitation has been observed when low scavenger concentrations were used in spent hydrochloric (HCl) acid. This paper provides optimum design parameters that allow for much effective use of H 2 S scavengers without causing the formation of calcium sulfide scale.