Fire Dynamics Simulator (FDS) is a computational fluid dynamics model used to calculate fire phenomena. The use of computer models such as FDS is becoming more widespread within the fire engineering community. Fire engineers are using computer models to demonstrate compliance with building codes. The computer models are continuously being developed as fire science and computing technology advances. It is essential that these models are validated to the point were the fire engineering community can have confidence in there use. This research report analyses FDS predicted sprinkler activation times with actual sprinkler activation times from a series of chair fires in a 8 x 4 x 2.4 meter gypsum wallboard compartment. The experiments consisted of a series of chair fires where the mass loss rate and sprinkler activation times were recorded, as well as temperature data. The fire data, compartment details and sprinkler head details were then modelled in FDS. The research shows that the c-factor values used by the sprinkler activation model in FDS has a significant influence. The c-factor value influenced the sprinkler activation times by as much as 50 %. FDS predicted sprinkler activation times with varying degrees of success. The success depended on the sprinkler head type modelled and position of the fire. The grid size used for the simulation affected the sensitivity of the comparison.