Preferred Label : coefficient of haze;
Detailed label : coefficient of haze (COH) in atmospheric chemistry;
IUPAC definition : One technique of measurement of the amount of filterable particulate matter suspended
in air which has been used in the past depends upon drawing a measured sample of air
(usually 1 000 linear feet) through a paper or membrane filter. A measurement is made
of the intensity of light transmitted through the dust spot formed relative to that
transmitted through an identical clean filter. The dirtiness of the air is reported
in terms of the COH unit. This relates to the quantity of particulate material which
produces an optical density, \[\log _{10}(\frac{I_{0}}{I})\] of 0.01 when measured
by light transmission at 400 nm and relative to the transmission of an identical dust-free
filter taken as 100%. Thus a filter which transmitted 50% relative to the clean filter
has an absorbance of 0.301 or 30.1 COH units. This is not a recommended measure of
filterable particulate matter since the size, colour and other properties of the aerosol
and the air in which it is suspended affect the results.;
Origin ID : C01125;
See also
One technique of measurement of the amount of filterable particulate matter suspended
in air which has been used in the past depends upon drawing a measured sample of air
(usually 1 000 linear feet) through a paper or membrane filter. A measurement is made
of the intensity of light transmitted through the dust spot formed relative to that
transmitted through an identical clean filter. The dirtiness of the air is reported
in terms of the COH unit. This relates to the quantity of particulate material which
produces an optical density, \[\log _{10}(\frac{I_{0}}{I})\] of 0.01 when measured
by light transmission at 400 nm and relative to the transmission of an identical dust-free
filter taken as 100%. Thus a filter which transmitted 50% relative to the clean filter
has an absorbance of 0.301 or 30.1 COH units. This is not a recommended measure of
filterable particulate matter since the size, colour and other properties of the aerosol
and the air in which it is suspended affect the results.
