Sections 1 - 4 of ANSI/SEI 104-1998 are as follows:

1. Purpose, Practice, Rationale and Scope
2. Determination of Standard Compliance
3. References
4. Definitions

Sections 5 and 6 describe the test method and procedures of validation. Descriptions and related data follow.

Stock standard gas was created by static dilution from 100% analyte, mixed volumetrically with input air pumped at a pre-set flow rate through an inert polypropylene chamber containing Diffusive Samplers under test. Flow was verified by in-line rotameter and analyte concentrations were verified by charcoal tube samples continuously drawn from locations in the chamber bracketing the Samplers under test. Assay Technology Sampler No 548 incorporating a polyacetal Sampling Grid with four (4) tubular sampling channels, a 200 mg charcoal (coconut) wafer, and a Wafer Dish and Sampler Cap made of polyester.

Analyte recovery and de-sorption efficiency determined by analysis (Method AT541) of charcoal wafers "spiked" from standard analyte solutions in methylene chloride. Samplers were tested at several "spike" levels cor-responding to levels expected for 8-hr Sampler exposures at 0.1-2.0 times the internal Exposure Limit (EL) of 300 ppm. An average recovery for this chlorofluorocarbon from the Assay Technology charcoal sampler was 96%, over the range of 50-200 m g/sample. Results in Table 6.2.

(De-Sorption Efficiency)

Samplers were subject to chamber exposures as described in Section 5. then analyzed by Method AT541. Exposures were applied to Samplers in the range 1-8 hours and 0.1-2.0 times the EL of 300 ppm. For this evaluation, the sampling rate for this Chlorofluorocarbon using the Assay Technology sampler was determined to be 0.50 ml/minute. Results in Table 6.3.

Samplers were subject to Exposure Pulse (> OSHA PEL) with a duration less than 50% of the Recommended Sampling Time (RST) followed by a Zero Exposure Period (ZEP) for the duration of the RST. The recovery of analyte from Samplers analyzed immediately following Exposure Pulse was compared with analyte recovery from identically-exposed Samplers analyzed at the end of the RST (i.e. following the Zero Exposure Period). The difference between these two recoveries is taken as the extent of Reverse Diffusion (i.e. evaporative loss as % of Sample) from the Sampler under the experimental conditions chosen.

In practice, Bias Due to Reverse Diffusion will depend on the extent and duration of actual Exposure Pulses in the environment being monitored which cannot be exactly predicted in a lab test. For this evaluation, Bias Due to Reverse Diffusion was estimated as the extent of Reverse Diffusion (evaporative loss as % of Sample) when an Exposure Pulse at 1.0 times the EL is applied for 25% of the duration of the RST (2 hr) followed by a Zero Exposure Period of 100% of the RST (8 hr). Results in Table 6.4.

After Zero Exposure Interval