Programa De Seguridad Y Salud En El Trabajo

AMMONIA IN WORKPLACE ATMOSPHERES - 
SOLID SORBENT


[pic]
Method No.:
ID-188




Control No.:
T-ID188-FV-02-0201-M




Matrix:
Air




OSHA Permissible Exposure Limits*
   Final Rule Limit (ammonia):
   Final Rule Limits
      (ammonium chloride fume):
   (ammonium chloride fume or
      ammonium sulfamate):*
35 ppm [Short-Term Exposure Limit (STEL)]
20 mg/m3 STEL*10 mg/m3 [Time Weighted Average (TWA)]*




Transitional Limit:
50 ppm TWA




Collection Device:
For ammonia collection, a personal sampling pump is used to draw a known volume of air through a glass tube containing carbon beads impregnated with sulfuric acid (CISA).




Recommended Sampling Rates
   TWA Determinations:
   STEL Determinations:
Ammonia
0.10 liter per minute(L/min)
0.5 L/min




Recommended Air Volume
   TWA:
   STEL:
Ammonia
24 L
7.5 L




Analytical Procedure:
The sample is desorbed with deionized water and analyzed as ammonium ion using an ion chromatograph.




Detection Limits Qualitative:
Ammonia
0.60 ppm (24-L air sample)
1.9 ppm (7.5-L air sample)




Quantitative:
1.5 ppm (24-L air sample)
4.8 ppm (7.5-L airsample)




Precision and Accuracy
   Validation Range:
   CVT:
   Bias:
   Overall Error:
Ammonia
30.7 to 101.8 ppm
0.050
-0.009
±10.9%




Method Classification:
Validated Method




Chemist:
Date (Date Revised):
Robert G. Adler
1987 (January 2002)




* Note:
Ammonium chloride fume or ammonium sulfamate can be sampled and analyzed using this method. Amixed-cellulose ester filter, polystyrene cassette, and personal sampling pump (2 L/min) are used to collect the sample. Samples are analyzed by ion chromatography after resorption in deionized water.






[pic]


Commercial manufacturers and products mentioned in this method are for descriptive use only and do not constitute endorsements by USDOL-OSHA.  Similar products from other sources can besubstituted.

[pic]


Branch of Inorganic Methods Development
OSHA Technical Center
Salt Lake City, Utah

1. Introduction

This method describes the sample collection and analysis of airborne ammonia. Ammonium chloride fume or ammonium sulfamate can also be analyzed using this method. Samples are taken in the breathing zone of workplace personnel and are analyzed by ionchromatography (IC). 



1.1 History

1.1.1 Sampling:

The previous OSHA sampling procedure for ammonia involved the use of a midget fritted glass bubbler containing 0.1 N sulfuric acid (H2SO4) (8.1, 8.2). Bubbler sampling is inconvenient to use. It involves the use of a liquid which if spilled may be irritating to the skin or may damage sampling pumps. Also, the sample solutionsmay leak during shipment.

The present method employs glass tubes containing CISA which avoids liquid sampling media problems. It is based on a procedure described by Bishop, et. al. (8.3).

1.1.2 Analysis:

Two analytical procedures have previously been used by OSHA. In the earliest procedure, ammonia was analyzed by a colorimetric method using Nessler reagent (8.2, 8.4).This method has significant interferences. The most recent method involved the use of the ammonia ion specific electrode (ISE) which does not discriminate between ammonia and amines (8.1).

The present method provides an analytical procedure which is easily set up and automated. Partial processing of the data is performed while the analysis is in progress.

1.1.3. An alternatescreening technique for measuring ammonia exposures in the workplace involves the use of detector tubes (8.5). Other methods are needed to determine long-term ammonia concentrations since short-term detector tubes offer only spot checks of the environment.


1.2 Principle

A known volume of air is drawn through a sampling tube containing carbon beads impregnated with sulfuric acid...