Page:NIOSH Manual of Analytical Methods - 6700.pdf/4

 NITROGEN DIOXIDE: METHOD 6700, Issue 2, dated 15 January 1998 - Page 4 of 5 [6] [7]

Bartley DL, Doemeny LJ, Taylor DG [1983]. Diffusive monitoring of fluctuating concentrations. Am Ind Hyg Assoc J 44:241-247. Hearl FJ, Manning MP [1980]. Transient response of diffusive dosimeters. Am Ind Hyg Assoc J 41:778-783.

METHOD REVISED BY: Frank Hearl, NIOSH/DRDS; Mary Lynn Woebkenberg, NIOSH/DPSE.

APPENDIX: PREPARATION OF SAMPLER 1. Measure the average cross-sectional area of a length of 3/8 inch (9.5 mm) ID acrylic tubing. a. Cap one end of the tubing. Pour in a known volume, v (mL), of water to nearly fill the tubing (e.g., 100 mL water for a 180-cm (6-foot) length of tubing). b. Measure the height, h (cm), of the water column in the tubing. 2 c. Determine the average cross-sectional area, A t (cm ), of the tubing.

At

v h

2. Cut the tubing into lengths, L (ca. 7.1 cm), such that A t / L = exactly 0.1 cm. NOTE: The collection rate is directly proportional to A t / L. For At / L = 0.1 cm, the collection rate is 2.3 nanomoles/ppm-h [2]. 3. Cut circular portions, 13/32 inch (10.3 mm) to 7/16 inch (11.1 mm) in diameter, from stainless steel screen using a 13/32 inch (10.3 mm) paper punch or other suitable means. 4. Clean the tubes, screens and caps with detergent solution in an ultrasonic bath. Rinse with distilled water. Air dry. 5. Dip the screens in absorbing reagent. 6. Using forceps, place the screens on absorbent paper. Press the screens momentarily with the forceps tips to blot. Allow the acetone to evaporate. 7. Stack three treated screens in the bottom of an unflanged cap. Insert the acrylic tube into the unflanged cap securing the screens (see the figures). 8. Slide the pen clip onto the acrylic tube touching the unflanged cap. Secure the pen clip and unflanged cap with a piece of electrical tape. 9. Apply a small amount of stopcock grease to the outside of the uncapped end of the acrylic tube and slide the flanged cap into place.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition