Method 18 has several specific and unique analytical components, which are outlined below. These requirements should be followed unless specific approval has been obtained by the oversight agency.

• Pre-analytical Survey: A sample from a source will be sent to the laboratory for a preliminary analysis. The results from the preliminary analysis will determine the calibration range as well as determine the concentrations of post spike target pollutants used in the matrix recovery study. A separate pre-analytical survey is completed for each source. The survey does not need to be repeated by the laboratory unless significant changes to the source stream have been made.
• Target Pollutant Recovery Study: Results from this study determine the hold-time and bias for the target pollutants for each source. The study will evaluate 1 day, 2 day, 3 day and 5 day hold-times for the target pollutants in Tedlar bags. The study will also determine correction factors if required for target pollutants. These correction factors will be maintained by the laboratory and applied to the sample analysis data. A separate recovery is required for each source. The recovery study does not have to be repeated by the laboratory unless significant changes to the source stream have been made. This component would not be required when using Summa canisters.
• Audit Sample: The analysis of an EPA audit sample is conducted and must be within 10% of the prepared value. If the EPA audit sample is not available, a second source laboratory calibration standard (LCS) is prepared. The LCS is required to be within 10% of the prepared value.
• Sample Analysis: The method calls for 3 samples to be collected in Tedlar bags for each sampling event. The 3 samples will be analyzed in triplicate by the laboratory.
• Quality Control: The laboratory will be responsible for following the quality control as specified in 40 CFR Part 60 Appendix A, including a three-point initial calibration run in triplicate and an end-check standard run in triplicate.
• Some test plans may allow for modification to Method 18, which can reduce the analytical costs. Modifications can include eliminating the pre-analytical survey or the target pollutant recovery study, and should be considered when designing a test plan.