British Standards Relevant to Agriculture

British Standard Summaries

BS2742: 1969 (confirmed 1991)
Use of the Ringelmann and Miniature Smoke Charts 


The text herein is not a a full reproduction of the British Standard. It is summary based upon interpretation of the original text and not intended as a replacement for the full text. It should be used for general guidance only.

Smoke emissions may be visually assessed by comparing the darkness of the smoke with standard shades of white (0) through to black (5) on a chart placed in a suitable position. Each shade represents 20% obscuration of the background. This technique was developed by Professor Ringelmann towards the end of the last century.

Both charts are available from British Standards publications. Once obtained, it should be mounted on a support such that its is held firmly without creases or bending. Any holding material must be of neutral colour. No protective covering should be placed over the chart as the shades may be distorted by light reflection.

The chart should be used in daylight and placed facing the observer in a vertical position. The chart should be placed such that it appears in line with the top of the stack. It should be at sufficient distance from the observer for the lines to appear to merge until each square forms a uniform shade. This is usually around 15 metres or more from the observer.

Diagram illustrating the use of the Ringelmann smoke chart.

The darkness of the smoke at the point where it leaves the stack should be compared with the shades on the chart. Estimates of the shade to the nearest quarter Ringelmann number should be made. The time of duration of the dark smoke should also be noted. The darker the smoke the greater the polluting potential of the smoke. The diagram below illustrates how the charts are used.

In the majority of situations the Ringelmann Chart is adequate, however it does require either a second person to assist the observer by holding the chart vertical or it will require securing to a building or similar. Where this is not possible the BS Miniature smoke chart may be used. This is not considered as accurate as the Ringelmann chart but is often useful for a preliminary measurement.

The shades on the chart are the same as that on the Ringelmann chart but it has been designed to be used at a distance of less than 2 metres from the user so could be used at arms length. For detailed information on both charts see the full Standard available from the British Standard Institution.

The 1972 addendum to this standard explains the calibration of instruments in Ringelmann number.

A British Standard nor this summary does not, necessarily, include all the necessary information for correct implementation of the Standard to any specific application. This is purely the responsibility of the user. Standards are updated by either amendment or revision. Users should ensure that they are using the latest version.


The full text of this Standard can be obtained from the British Standard Institution

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