Chapter 4 Calibration
4-7
2. Periodically challenging the Model 48C with a CO level of approximately 80% of
the URL. The 80% URL level may be obtained by dilution of a higher level of CO
using a system similar to that of Figure 4-1, or by using a low level cylinder of CO
containing CO in air at a concentration of approximately 80% of the URL. In either
case the cylinder of CO should be checked against an SMR or CRM. It should also
be true for a cylinder of low level CO. The Quality Assurance Handbook
1
should be
referred to for the procedure of checking the cylinders. Record the Model 48C's
response in % of scale as A
80
. Compute the span error from the following equation:
Span Error, % = ([A
80
- Z)URL/100] - [CO]) X 100/[CO]
Where:
Z = Recorder response obtained at the last calibration for zero air, % scale.
[CO] = Span concentration
3. Latest copy of the Quality Assurance Handbook for Air Pollution Measurement
Systems
1
should be consulted to determine the level of acceptance of zero and span
errors.
4. For detailed guidance in setting up a quality assurance program, refer to the Code of
Federal Regulations
3
and the EPA Handbook on Quality Assurance
1
.
REFERENCES
1. QUALITY ASSURANCE HANDBOOK FOR AIR POLLUTION
MEASUREMENT SYSTEMS, Volume II - Ambient Air Specific Methods EPA
600/4-77-027a, May 1977 and 40 CFR 50, Appendix C.
2. Available from Purafil, Inc., POB 80434, Atlanta, GA 30366.
3. 40 CFR 58, Appendix A, B.
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