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 in two ways: (1) Flash Evaporation Method - by passing a solution of glycol ether in alcohol through a heated stainless steel capillary at a flow rate controlled by a liquid syringe pump. (2) Vapor Pressure Method - by passing air at a controlled flow rate over a vessel of neat liquid maintained at a controlled temperature. In both cases, evaporate was then passed into a stream of make-up air (at controlled temperature, flow rate, and humidity) provided by a Miller-Nelson controller into an inert polypropylene chamber containing Diffusive Samplers under test. Flow was calibrated by direct measurement, and analyte concentrations were verified by charcoal tube samples continuously drawn from locations in the chamber bracketing the Samplers under test.

Analyte recovery and de-sorption efficiency determined by analysis (Method AT541) of charcoal wafers "spiked" from standard analyte solutions in 90% methylene chloride/10% methanol. Samplers were tested at several "spike" levels corresponding to the range of levels expected (1-5 ppm) for 4-8 hr Samples. Results in Table 6.2.

(De-Sorption Efficiency)

Table 6.2

(a) De-Sorption Method = Forward

(b) De-Sorption Solvent = 97% Carbon disulfide + 3% Benzyl alcohol

(c) De-Sorption Volume = 2 ml

(d) Media = Assay Technology AT541

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 in the range 1-10 ppm. Results in Table 6.3.

NMP = N-Methyl Pyrrolidinone

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 PEL is applied for 12% of the duration of the RST followed by a Zero Exposure Period of 100% of the RST. Results in Table 6.4.

After Zero Exposure Interval

(% Loss = "Reverse Diffusion")

Reverse Diffusion Challenge

NMP = N-Methyl Pyrrolidinone

Unexposed Samplers analyzed by Method AT541 to determine background Analyte levels (if any) on the Sampler prior to sampling. No detectable levels of either glycol ether or NMP were found.

Samplers have been exposed to atmospheres of benzene, toluene, and xylene for 2-4 hrs at 1-2 times the OSHA PEL in a Chamber with 3 zones of different cross-sectional areas such that linear velocities of 15, 50, and 150 cm/sec, respectively, were generated. Samplers were placed in each zone with 50% of samplers placed normal to and 50% of Samplers perpendicular to the flow direction. When data were compared from the six locations (representing normal air velocity and orientation variation in workplaces), no significant differences were found among the six groups indicating the absence of an effect of Air Velocity & Orientation on Sampling Rate in the range 15-150 cm/sec. This result is applicable to other organic vapors when the same Sampler is used.

Samplers have been exposed to atmospheres of benzene, toluene, and xylene for 2-4 hrs at 1-2 times the OSHA PEL (as per Section 5.) in several Chamber runs in which nearly identical exposures were applied with variations in temperature and humidity as follows: 22^oC/50%RH, 10^oC/50%RH, 30^oC/30%RH, 30^oC/70% RH. Data from the four conditions (representing normal temperature & humidity variation) showed no significant differences among the groups indicating the absence of an effect of Temperature & Humidity on Sampling Rate in the range 10-30^oC and 30-70% RH. This result is applicable to other organic vapors when the same Sampler is used.

Ethylene Oxide Samplers (Monitor 502) in sealed packaging exposed to >10 ppm ethylene oxide for >2 hours, then analyzed as directed in the Instructions for Use. Results from analysis were not significantly different from results for un-exposed Samplers (blank values) demonstrating the integrity of Sampler packaging. This result with ethylene oxide (which has highest permeability through plastics and pinholes of all analytes tested) is applicable to all Samplers manufactured by Assay Technology and packaged in its standard aluminum foil pouch.

Monitor 541 incorporates a collection wafer made from coconut charcoal demonstrated to collect upwards of 200 volatile organic compounds. The likelihood of a Sampler's collecting interfering substances is addressed by an analytical method (capillary gas chromatography) which can separate and analyze 100's of VOCs. A method has been developed utilizing a high-resolution capillary columns (30 m x 0.53mm) providing identification of analyte from its characteristic emergence time on the analytical column and quantitation of analytes by peak area

GC Conditions used were as follows:

HP-1 (methyl silicone) - 0.88 m m coating thickness on a 30m x 0.53 mm column

Inj Temp = 250oC Det Temp = 280oC Column Split Ratio = 4 to 1

Temp Program - 60oC/1 min hold ... 30deg/min to 200oC ... 0.34 min hold ... 6.0 min run

Three groups of Samplers from separate manufacturing Lots subject to three exposure tests (see Section 5.) including benzene, toluene, and xylene for 2-4 hrs at 1-2 times the PEL. When data from the three Lots were compared in each of the three exposures, no significant differences were found among the groups indicating the absence of differences among different Lots of Samplers. This result applicable to other volatile organic analytes sampled on Monitors 541 and 546.

Sampler 541 has been evaluated for sampling Glycol Ether and N-Methyl Pyrrolidinone on a single sampler. Recovery, Reverse Diffusion, and Sampling Rates studies indicate that both analytes can be recovered quantitatively from the sampler, and no detectable loss of analyte was found during sampling. The measured Sampling Rate for Glycol Ether was found in limited experiments to be within 3-6% of the manufacturer's stated Uptake Rate of 3.51 ml/min. Variation is these studies was greater than normal due non-homogeneity in the exposure chamber arising form the difficulty of vaporizing Glycol Ether.

Based on estimated variations of + 5% in Sampler-to-Sampler variation, +3% in Analytical Lab, and an uncertainty of +10% in Uptake Rate, the overall accuracy is estimated to be within +18% of the true value.