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The air
quality directives obligate municipalities to monitor their air quality and to
report the results of monitoring to citizens and to spread hourly based
concentration data e.g. in the internet. In a case when the concentrations
exceed the limit values, a city has to take measures to reduce pollution, e.g.
by reducing the traffic. It is of a great importance that the kind of decisions
will be based on reliable air quality data. For that reason the quality
assurance is a major part of the air monitoring activity. Only by quality
assurance the measured results can be guaranteed. False results can lead to the
wrong conclusions, which is not desirable.
Quality
assurance means all the planned activities that are necessary to full fill all
the requirements set for the air quality monitoring. The goals of the quality
assurance are reliability, accuracy, repeatability, comparability and validity
of the air quality data. Quality assurance should cover all the activities
related to the air quality monitoring, e.g. planning of air quality monitoring
system, monitoring the air quality, preventive maintenance of the analysers,
calibration, data handling and documentation, reporting of air quality and
qualification of the staff working with the air quality monitoring system.
In the Turku region the quality system was
built in 1997 – 1998. The whole process of quality assurance is described in
the quality handbook. In practice the quality work is based on the careful and
right-timed service of the analysers. In order to get reliable results the gas
analysers are calibrated automatically once a day by using the permeation oven.
By the automatic calibration zero and span values are checked. Furthermore a
monthly calibration is required. Normally one concentration combined with zero
and span value checks is adequate in monthly calibration. If the one-point
calibration differs a lot from the last calibration it is necessary to perform
a multi-point calibration when four different concentrations are checked. Once a year an independent calibration is used in order to make
sure that our portable calibrator functions correctly. An independent
party performs the calibration of particulate analysers once a year. It is also
a possibility to buy calibration services from the National Reference
Laboratory.
The
results from the air quality monitoring in Turku region have been reliable.
Analysers have been very stabile so far. In daily calibrations the zero values
vary only a little. The validity of the results has been extremely high (94 –
99 % in the year 2003). Because the air quality measuring in
total are functioning very well it is possible to concentrate to the
other aspects of the quality assurance such as the reporting and informing of
our results. |