SCALE FOR THE MEASUREMENT OF THE OPACITY OF DUST EMISSION INTO THE ATMOSPHERE
No. 1 No. 2 No. 3 No. 4
MINISTÈRE DE L’ENVIRONNEMENT
GOUVERNEMENT DU QUÉBEC
(1) Select an observation point situated more than 30 m and less than 400 m from the source of emission.
(2) Avoid looking toward the sun and select an observation angle free of dark objects in the background.
(3) Hold the chart at arm’s length and look at the emission through the slit.
(4) Record the scale number that best corresponds to the opacity of the emissions at each observation.
(5) To calculate the opacity of an emission, record shades of opacity from at least 4 observations, using the following formula:
P = NEU at opacity No. 1 X 20%
number of observations
where P represents the percentage opacity of the emission and NUE the number of equivalent units.
The number of each numbered shade constitutes the same quantity of equivalent units.