Particulates of many substances which can cause pulmonary fibrosis and other ill effects when they are deposited in the alveoli are identified as the respirable fraction of inhaled airborne particulate. This work reviews the research which led to the determination of the particle sizes of respirable particulate and of the standard definitions of those sizes which were used to guide the development of size‐specific air sampling instruments. The historical development of such instruments from the period before the First World War when samplers used the human lung as air‐movers through the late 20th century which saw the introduction of real‐time instruments which continuously measured full‐shift airborne respirable dust concentrations in the breathing zones of workers. The dimensional definitions of respirable fibrous particulates such as asbestos are discussed as well as the instrumentation and measurement procedures. Proposals are made for personal dust measurements using the remote sensing of airborne dust concentrations coupled with wireless devices to locate workers within a dust cloud.