CALIFORNIA AIR RESOURCES BOARD
Auditorium, First Floor
400 "P" Street
January 12, 1989
89-1-1 Public Hearing to Consider Amendments to 001
Regulations Regarding the Standard for Visibility
Reducing particles and Measurement Methods for
Determining Ambient Concentrations of Visibility
89-1-2 Status Report on Staff Activities Regarding Air 199
Pollution in the San Joaquin Valley.
Public Hearing to Consider Amendments to Regulations Regarding
Measurement Methods for Determining Ambient Concentrations of
Visibility Reducing Particles and Restatement of the Standard.
The Board staff proposes regulatory amendments to establish a
specific sampling method for purposes of monitoring for
compliance with the air quality standards for visibility reducing
The proposed Method V is a combination of an integrating
nephelometer for measuring light scattering at 550 nm wavelength;
a coefficient of haze (COH) tape sampler for measuring light
absorption; and a hygrometer or relative humidity probe to
document ambient relative humidity. ARB method V will set forth
performance specifications, operating, and calibration methods
for integrating nephelometers, coefficient of haze tape samplers,
and recording hygrometers.
Other sampling methods may be used for purposes of monitoring for
compliance with the visibility reducing particle standards if
they are shown, to the satisfaction of the ARB to give results
equivalent to the specified method at or near the level of the
Other amendments proposed by the staff include: changing the
duration of averaging period from one observation to 8 hours (9
a.m. - 5 p.m. Pacific Standard Time); deletion of the definition
of "Prevailing Visibility"; addition of definitions of "Visual
Range" and "Extinction Coefficient"' and amendments to the
definition of "Visibility Reducing Particles".
Amendments also restate the current standards in terms of the
specific extinction coefficients nominally equivalent to 10- and
30-mile visual range.
In its September 5, 1986 meeting, the Board adopted Resolution
86-86, which directs the staff to recommend an instrumental
monitoring method for measurement of visibility degradation, and
restate the current statewide and Lake Tahoe Air Basin standards
in terms of that measurement.
The staff believes that the integrating nephelometer and the
coefficient of haze tape sampler, when operated in accordance
with the appropriate quality control procedures, will provide
accurate and reliable visibility reducing particle measurements.
The relative humidity measurement is needed to apply the 70%
relative humidity cutoff which is part of the definition of the
SUMMARY AND IMPACTS
The staff believes that there are no significant environmental or
cost impacts or issues of controversy regarding the proposed
adoption of a visibility reducing particle sampling method and
associated performance criteria.