This device detects the optical photons generated by alpha particles in air, thus having a far greater range. Alpha particles can cause ionisation of nitrogen in air, which in turn produces fluorescence photons that show up as discrete spectral lines in the UV band of the electromagnetic spectrum. These photons can travel much further than alpha particles and are not hindered by surface particles or roughness and can be transmitted through any UV transparent material such as plastic or glass. This means an area could be made safe before a contamination assessment is carried out.