Prototype sampling system for measuring workplace protection factors for gases and vapors

Criteria for the collection of useful respirator performance data in the workplace

Workplace protection factors (WPFs) are intended to measure the ability of a respiratory protective device (RPD) to reduce contaminant exposure when used in the context of an effective respiratory protection program. In 1992, members of the American Industrial Hygiene Association Respiratory Protection Committee (RPC) published a review of important issues and considerations for measuring respirator performance in the workplace. The RPC recognized that respirator testing in workplaces can have a variety of objectives and endpoints, and that not all workplace measurements are WPFs. That paper addressed concerns in the general categories of 1) study objectives; 2) site selection; 3) subject selection and preparation; 4) sampling and analytical methods; and 5) data analysis. No specific protocol for measuring WPFs was recommended by the RPC, and attempts to reach a U.S. consensus on a WPF protocol since 1992 have not succeeded. Numerous studies have implemented the principles for WPF measurement described in the RPC paper. Modifications to the original recommendations have been made to reflect the current state of the art. This article describes what has been learned in recent years in each of the five categories identified in the 1992 discussion. Because of the wide variety of workplaces and work activities, contaminants and respiratory protective devices, a strict protocol is not appropriate for collecting WPF data. Rather, the minimum requirements for the collection and presentation of meaningful respirator performance data in the workplace are described. Understanding of these principles will permit useful RPD performance data to be generated.

Evaluation of a fluorometric method for measuring low concentrations of ammonia in ambient air

A fluorometric method developed for measuring low concentrations of ammonium in marine and freshwater ecosystems was adapted for the analysis of ammonia in ambient air. The modified method entails collection of samples on an acid-treated solid adsorbent followed by analysis using a fluorometer. Optimal results were obtained using a commercially available sorbent tube containing 100 mg of acid-treated silica gel for sample collection, and an analytical protocol consisting of sample desorption in DI water, addition of orthopthaldialdehyde (OPA) working reagent, and room temperature incubation. Method accuracy and precision were evaluated by comparing experimentally determined quantities of ammonia to expected levels for sample loadings ranging from 0.16 [micro sign]g to 550 [micro sign]g-accuracy was generally within +/-20%. The estimated LOQ for the method is 0.08 [micro sign]g ammonia per sample which represents a 25-375-fold improvement in sensitivity compared to current NIOSH and OSHA methods for the measurement of ammonia in ambient air. The new method should be useful for applications requiring measurement of low concentrations of ammonia using personal sampling equipment or in the characterization of short-term fluctuations of ammonia concentrations in air.