Subpart Z
The recommended sampling rate is 0.05 L/min for 1 hour, giving a total air volume of 3 L as specified in Appendix D to 1910.1051.
Sampling tubes must be 5-cm silane‑treated glass tubes (4 mm ID × 6 mm OD) packed with two sections of specially cleaned charcoal coated with 4‑tert‑butylcatechol (TBC): a 100‑mg front (sampling) section and a 50‑mg backup section separated and retained with silanized glass wool plugs, and sealed with plastic end caps, per Appendix D to 1910.1051.
Because TBC is a polymerization inhibitor that greatly improves the stability of low‑level BD samples, the method requires coconut‑shell charcoal specially cleaned and coated with 4‑tert‑butylcatechol to prevent BD loss and polymerization during storage, per Appendix D to 1910.1051.
Collected samples should be sealed with plastic end caps, wrapped lengthwise, and stored frozen if they will be held before laboratory analysis; if exposed to higher than normal ambient temperatures during transport, refrigerate them. Upon receipt at the laboratory samples should be placed in a freezer, according to Appendix D to 1910.1051.
The detection limit of the overall procedure is 90 ppb (200 µg/m3) and the reliable quantitation limit is 155 ppb (343 µg/m3), both based on a 3 L air volume, as stated in Appendix D to 1910.1051.
Breakthrough is defined as the relative amount of analyte found on the backup section compared to the total amount collected on the tube; in the method's study, 5% breakthrough occurred after sampling a 2.0 ppm BD atmosphere for 90 minutes at 0.05 L/min (4.5 L sampled), per Appendix D to 1910.1051.
Attach the sampling tube in the worker's breathing zone in a vertical manner such that it does not impede work performance, with the larger front section exposed directly to the atmosphere and no tubing placed ahead of the sampling tube, as required by Appendix D to 1910.1051.
Transfer the 100‑mg (front) section and the 50‑mg (backup) section to separate 2‑mL vials, add 1 mL of carbon disulfide to each vial, seal with Teflon‑lined caps, and desorb for one hour with vigorous manual shaking several times during that hour, according to Appendix D to 1910.1051.
The method recommends using a gas chromatograph with a flame ionization detector (FID) and the following conditions: column temperature 95 °C; injector 180 °C; detector 275 °C; carrier gas flow 30 mL/min; injection volume 0.80 µL; and a 20‑ft × 1/8‑in OD stainless steel column containing 20% FFAP on 80/100 mesh Chromabsorb, as specified in Appendix D to 1910.1051.
You calculate BD air concentration in mg/m3 using the equation mg/m3 = (A)(B)/(C)(D), where A = µg/mL from the chromatogram, B = desorption volume (mL), C = liters of air sampled, and D = desorption efficiency; then convert mg/m3 to ppm with ppm = (mg/m3)(24.46)/54.09, per Appendix D to 1910.1051.
During sampling, attach equipment so it doesn't interfere with work, and follow all applicable safety practices for the work area; for analysis, avoid skin contact and inhalation of chemicals, work in a fume hood when possible, and wear safety glasses and a lab coat, as advised in Appendix D to 1910.1051.
The average desorption efficiency reported for BD from TBC‑coated charcoal over 0.6 to 2 times the target concentration was 96.4%, according to Appendix D to 1910.1051.
Prepare 30 g batches by stirring charcoal with 10% phosphoric acid for one hour, filtering and washing to remove acid, heat‑treat the washed charcoal at 700 °C under nitrogen for at least 1 hour, cool, add TBC equal to 10% of the charcoal weight, then heat the charcoal‑TBC mixture at 60 °C for 1 hour in a water bath; finally cool and store the coated charcoal in a sealed, dark container segregated by lot number as described in Appendix D to 1910.1051.
Prepare standards by injecting known volumes of BD gas into the headspace above 1 mL of carbon disulfide in sealed 2‑mL vials, shake after injection, and prepare a calibration curve daily by plotting detector response versus concentration and curve fitting, per Appendix D to 1910.1051.
The sampling method reports no known sampling interferences, but analytically any compound with the same retention time that gives a detector response is a potential interference; the method recommends changing GC parameters or using GC/MS to confirm sample identity when possible, as noted in Appendix D to 1910.1051.
The method's target concentration is 1 ppm, which is equivalent to 2.21 mg/m3 (referenced to 25 °C and 760 mm Hg), as specified in Appendix D to 1910.1051.
The detection limit of the analytical (instrumental) procedure used in the evaluation was 304 pg per injection, as reported in Appendix D to 1910.1051.
Include at least one blank per sampling set handled identically except no air drawn; perform blank corrections before adding amounts from the front and backup sections and before calculating air concentrations, per Appendix D to 1910.1051.
If both expected BD concentration and relative humidity are high, reduce the sampling time from 60 minutes to 45 minutes (keeping the sampling rate at 0.05 L/min) to limit breakthrough, as recommended in Appendix D to 1910.1051.
Store packed sampling tubes in a sealed container in the dark at room temperature and segregate tubes by coated adsorbent lot number; save used sampling tubes so they can be cleaned and repacked with fresh adsorbent, as described in Appendix D to 1910.1051.
The method cautions that TBC is toxic and should be handled only in a fume hood while wearing gloves; similarly, carbon disulfide is used as the desorption solvent and standard preparation solvent and should be used in a fume hood with appropriate PPE, per the safety guidance in Appendix D to 1910.1051.
Yes—the method can be used at concentrations higher than the 1 ppm target, but sampling time should be reduced (for example to 45 minutes) when both BD levels and relative humidity are high to avoid breakthrough, as stated in Appendix D to 1910.1051.