National Institute for Occupational Safety and Health

“ The overall precision and accuracy have not been completely determined. In one experiment, the efficiency of bubbler collection of PCl 3 was found to be 0.99 ±0.06 based on six pairs of bubblers sampling from a 3.1 mg/m 3 atmosphere generated using a diffusion cell. At the concentrations studied, PCl 3 tended to react with water vapor in the air to produce fogs of H 3PO 3. ”

“ Attach the sample bag to the outlet port of the personal sampling pump with a minimum length of flexible tubing. (3) Pump the air sample into the bag at a rate calculated to fill ≤80% of the sample bag capacity over the sampling period. NOTE: The flow rate must be known to ±5% throughout the sampling period. (4) Within 24 hours after completion of sampling, introduce an aliquot of the sample into the GC (as in step 2a) . Obtain the carbon dioxide peak height of the injected sample. NOTE: Under these conditions, carbon dioxide elutes at about 2 min, after oxygen and nitrogen. ”

“ This method has undergone extensive laboratory evaluation for use in oxygen-deficient atmospheres and has been shown to be stable and reproducible [1] . The relative standard deviation, S r, for 15 different instruments monitoring the same atmosphere (under laboratory conditions) was 0.52% for over 100 readings over an 8-h period. The relative standard deviation, S r, for 18 different instruments monitoring the same atmosphere in field situations was 1.22% for 126 readings taken over a two-day testing period with calibration at the beginning of each day [1] . ”

“ A field study found results for this method of 109 ± 9% (mean ± sr) vs. a reference method in the range 12 to 19 ppm-h [3] . Sampling errors may exist in this method when the concentration is not constant in time and the sampling period is short [6, 7] . For example, the value of s r associated with estimating the TWA of an isolated random 10-sec concentration pulse within a 15-min sampling period may be calculated [6] to equal 0.5. Secondly, reference [6] reports a specific set of real-time concentration data measured in an industrial environment. ”

“ Transfer contents of the bubbler quantitatively to a 50-mL volumetric flask. Dilute to mark with distilled water and mix. NOTE: Start reagent blanks at this step. Pipet 25 mL of the diluted sample into a 50-mL beaker. Pipet 3 mL saturated bromine water into the beaker. Let stand 60 sec for oxidation to occur. NOTE: The purpose of the bromine water is to oxidize PCl 3, present in water as H 3PO 3, to H3PO 4. ”

“ Add 15 mL distilled water to the bubbler. Sample at an accurately known flow rate between 0.05 and 0.2 L/min for a total sample size of 11 to 100 L. NOTE: The bubbler must be kept in a vertical position during sampling. If the bubbler solution spills into the trap, discard the sample. Remove the bubbler stem and tap gently against the inside wall of the bubbler to recover as much of the sample solution as possible. Rinse the stem with several mL distilled water, collecting the rinse in the bubbler. Seal the bubbler bottom with a stopper. ”

“ 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. ”

“ Following manufacturer's instructions for this procedure, adjust readout meter to agree with the calibration standard.
NIOSH Manual of Analytical Methods (NMAM) , Fourth Edition, 8/15/94 OXYGEN: METHOD 6601, Issue 2, dated 15 August 1994 - Page 3 of 3 6.
Practice routine instrument maintenance. a. Check sensor cell diffusion barrier for dirt and moisture. Clean with a soft cloth or tissue if needed. b. Replace sensor cell every six to nine months with average use. NOTE 1: Store cell in nitrogen when not in use to prolong life. ”

“ Inject known volume of N 2O into the sample cell with a gas-tight syringe. NOTE: Inject the N 2O through tubing or a septum attached to the sample cell. c. Calculate concentration, C s (ppm) , of N 2O in sample cell:
d. When instrument reading stabilizes, record meter or recorder deflection. e. Prepare calibration graph (C s vs. meter or recorder deflection) . Practice routine instrument maintenance. a. Replace septa in a closed-loop system frequently in accordance with manufacturer's recommendations. b. Check and replace, if cloudy, the NaCl windows in the infrared spectrophotometer. ”

“ APPLICABILITY:The working range is 1.2 to 80 ppm-h [2] . The method is applicable for ceiling and short-term exposure measurements. In the development of this passive sampler, it was assumed that NO2 was completely converted to nitrite ion [1] . Incomplete conversion of NO2 to nitrite ion (Saltzman factor <1) will cause a negative bias [1] . Diffusive samplers have a lower collection efficiency at lower pressure (-7% @ 5500 m altitude) [4] .
INTERFERENCES:In very dusty environments, particles may deposit on the inside surface of the sampler. ”

“ SF 6* into sample bag containing a metered volume of clean air. Compressed argon or other gas* at approximately 30 psi for use as carrier gas.
See SPECIAL PRECAUTIONS.
1.
Portable gas chromatograph (GC) , with electron capture detector, gas sampling loop if desired (use of loop will limit variability of injection volume and therefore restrict range of method) , and strip chart recorder if appropriate. 2. Personal sampling pump, 0.02 to 1 L/mim or other rate suitable for filling sample bags, with flexible connecting tubing. NOTE: Pumps lubricated with petroleum products should not be used. ”

“ Aspirate a standard for every 10 samples to check instrument drift. Check recoveries with at least one spiked media blank per 10 samples. Use method of additions occasionally to check for interferences. ”

“ Battery life is two to six months for replaceable battery models. Some are equipped with nickel-cadmium batteries which require periodic recharging. Most operate at least 16 hrs without recharging. Some units have low-battery indicators. ”

“ Acetone is a fire hazard.
SAMPLING: 1. Attach the sampler with flanged cap down. Start sampling by removing flanged cap. Estimate appropriate sampling time such that the amount of NO 2 collected is in the range 1.2 to 80 ppm-h (0.13 to 8.5 μg NO2) . 2. Terminate sampling by replacing flanged cap.
CALIBRATION AND QUALITY CONTROL: 3. Calibrate daily with at least six working standards over the range 0 to 40 nanomoles (0 to 1.84 μg) NO2- per 2.1 mL combined reagent. a. Prepare working standards from calibration stock solution immediately before use. b. Allow 10 min for color development. c. ”

“ Woodfin WJ, Woebkenberg ML [in preparation] . An evaluation of portable direct-reading carbon monoxide monitors. Ashley K [1994] . Electroanalytical applications in occupational and environmental health. ”

“ Development of Methods for the Determination of Phosphoric Acid, PCl 3, PCl 5 and P 4S10 in Air, Final Report of NIOSH Contract 210-76-0038 (unpublished, May 10, 1977) . [2] NIOSH Manual of Analytical Methods, 2nd ed., Vol. 5, P&CAM 305, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 79-141 (1979) . [3] NIOSH/OSHA Occupational Health Guidelines for Chemical Hazards, U.S. Department of Health and Human Services, Publ. ”

“ The column used in the evaluation of this method was 38 cm x 0.6-cm (OD) stainless steel, packed with 100-120 mesh activated aluminum oxide, using an Argon carrier gas flow of approximately 30 mL/min. ”

“ This method may be used in work atmospheres to determine available O 2 levels and is particularly useful for determining safe entry conditions into confined work spaces. Many units are small enough to be worn on the person and may be used to obtain personal breat hing zone samples. ”

“ Combined reagent. Combine 1 part sulfanilamide solution, 1 part water, and 0.1 part NEDA solution. Protect from light and refrigerate. Stable ~ 1 month . 5. Sodium nitrite stock solution, 0.05 M. Accurately weigh 0.345 g NaNO2 (reagent grade) . Dissolve in 100 mL deionized water. Protect from light and refrigerate. Stable 90 days. 6. Calibration stock solution. Dilute an aliquot of NaNO2 stock solution with distilled water (e.g.,1:50 dilution yields1 nanomole NO2-/μL) . Prepare fresh immediately before use.
1. Sampler: See APPENDIX (Potential sources of equipment given in reference [1] ) : a. ”

“ OSHA : no standard NIOSH: 25 ppm ACGIH: 50 ppm (1 ppm = 1.80 mg/m 3 @ NTP)
Issue 1: 15 February 1984 Issue 2: 15 August 1994
PROPERTIES: gas; BP -88.46 °C; d = 1.53 (air =1)
SYNONYMS: hyponitrous acid anhydride; laughing gas. ”

“ Electrical tape, plastic. g. Stopcock grease. 2. Spectrophotometer, 540 nm, with 1-cm cuvettes. 3. Volumetric flasks and pipets for preparation of standards. 4. Mixer, vibration or vortex (optional) . 5. Forceps. ”