The Ringelmann scale is a scale for measuring the apparent density or opacity of smoke.[1][2] It was developed by a French professor of agricultural engineering Maximilien Ringelmann of La Station d'Essais de Machines in Paris, who first specified the scale in 1888.[3][4]
The scale has 5 levels of density inferred from a grid of black lines on a white surface which, if viewed from a distance, merge into known shades of grey. Shade 1 is slightly grey and is usually categorized by air pollution boards as acceptable. It corresponds to an opacity of 20%. Shades 2, 3, 4 and 5 correspond to opacities of 40%, 60%, 80% and 100% (completely black) and are usually considered to be "black smoke" by air pollution boards of most countries.[5]
- ^ IC 8333 - Ringelmann smoke chart (PDF). Washington, D.C.: United States Department of the Interior, Bureau of mines. 1 May 1967. Retrieved 31 August 2018.
- ^ "Sensing change: Maximilien Ringelmann Smoke Charts 1897". Science history institute. Retrieved 26 March 2019.
- ^ Hughes, Glyn (2010). "The Ringelmann smoke chart" (PDF). SOLIFTEC The Solid Fuel Technology Institute. Retrieved 31 August 2018.
- ^ Simon, Bernard (1998). "Max Ringelmann (1861-1931) et la recherche en machinisme agricole". In Fontanon, Claudine (ed.). Histoire de la mécanique appliquée enseignement, recherche et pratiques mécaniciennes en France après 1880. Paris: ENS Editions. pp. 47–55. ISBN 2-902126-50-6. Retrieved 26 March 2019.
- ^ Dark smoke - an introduction to air pollution control (smoke) regulations (PDF). Hong Kong: Environment protection department, Hong Kong. Retrieved 31 August 2018.