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The development of measurements and standardization of measurements
took mankind several thousand years. An object can be described
by its weight, length, area it occupies, density, etc. There
are several ways to measure the weight of the object. It can
be measured in terms of kilograms, pounds, tons, ounces, etc.
In the United States, the National Institute of Standards and
Technology standardizes the units of measurement.
The quality of the measurement depends upon the calibration and
units of the measuring device. For example, an imperial gallon
used to measure volume in Great Britain is not the same as the
U.S. gallon. In fact, the U.S. gallon is smaller.
Air Hygiene uses separate analyzers to characterize the emission
gases. Some of these gases include carbon dioxide (CO2), carbon
monoxide (CO), oxygen (O2), oxides of nitrogen (NOx), total hydrocarbons
(THC), sulfur dioxide (SO2), and hydrogen sulfide (H2S). The various
analyzers (O2, CO2, NOx, CO, THC, SO2) used at to quantify the
emissions have a tendency to drift as a function of time, pressure,
and temperature. Therefore, a calibration is performed at the beginning
of each day.
Calibrations are carried out on each measurement device according
to the schedule outlined by the Environmental Protection Agency.
The gases used to perform calibration have previously been tested
and certified for specific concentration as marked on the bottle
by the vendor. The vendor also provides a preparation date and
an expiration date along with the concentrations and the contents
of the gas bottle. A gas that has expired is not valid for calibration;
therefore, quality control is necessary.
At Air Hygiene, the emission testing analyzers are calibrated
at the beginning of each day, before testing. First, the analyzer
is set to zero concentration by sending Nitrogen gas or zero concentration
of the gas of interest. Second, the analyzer is once again adjusted
with the span concentration of gas of interest. Finally, the analyzer
is checked with one or two mid concentrations of gas. A linearity
test is performed to check whether the calibration was successful.
If the calibration does not pass the linearity test, the process
is repeated.
An erroneous calibration can lead to an erroneous test. Therefore,
quality control is necessary. At Air Hygiene, quality control checks
are also conducted in the field for each test program. The company
conducts air emission testing services per the requirements of
the Environmental Protection Agency and other relevant organizations
such as State Environmental Departments, the American Society for
Testing and Materials (ASTM) and the Gas Processors Association
(GPA). The company has a Standard Operating Procedures Manual and
a QA/QC program to establish accuracy of the testing results and
to insure confidence to the customer.
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