This dataset consists of ammonia (NH3) measurements from a set of ALPHA (Adapted Low-cost Passive High Absorption) sampler sites at Ballynahone National Nature Reserve, a designated Area of Special Scientific Interest (ASSI), Special Area of Conservation (SAC) and Ramsar (wetland of international importance designated under the Ramsar Convention) site in Northern Ireland. The park is an ammonia sensitive peatland ecosystem managed locally by Ulster Wildlife Trust (UWT). The data were originally collected due to concern that Ballynahone Bog may be adversely affected by NH3 emissions arising from local livestock installations.