What types and how many pathogens are we exposed to? Is our environment changing and impacting on our health? To answer these questions, we require various techniques to support our research, such as sampling, detection and identification, monitoring, transport models, and laboratory experimentation (Table 1) . Kuske reviewed the current and emerging technologies for the study of bacteria in outdoor air in 2006 [5] . We searched the literature from 2006 onwards to extend Kuske's review and paid close attention to the study of viruses. Some studies show that climatological factors can influence viral disease transmission, e.g. respiratory syncytial virus [6] . The environmental sampling of human viruses is therefore an area that we regard as important in order to prepare for new and emerging diseases in our time. Table 1 highlights the diverse skills and knowledge outside the traditional microbiology and aerobiology fields, which can be adopted to understand pathogens in the outdoor air. Kuske's review [5] contributes largely with regard to sampling and detection and identification in Table 1 . Our review has added, for example, the spatial and temporal monitoring issues, epidemiology and computational fluid dynamic models, and the application of laboratory experimental facilities. Moreover, a variety of examples were given on the study of viruses in the air.