This report describes the adaptation of an existing air sampling and analytical method for ozone to the personal monitoring of employee exposures to the substance inside a welding helmet.
The Saltzman iodometric method was modified to accommodate helmet sampling. The personal air sampler that was developed consists of a Teflon filter in a polystyrene holder joined with flexible tubing to a spill-proof impinger containing an alkaline potassium iodide solution.
The sampler is compatible with a personal sampling pump capable of an air flow rate of 2.0 L/min. The overall method was evaluated in the laboratory with â??110-L test atmosphere samples at an ozone concentration of about 0.1 ppm (0.2 mg/ m3 at 25° C) and with =40-L test atmosphere samples over the concentration range of 0.3 to 5.1 ppm (0.6 to 10mg/m3at25° C).
The average bias relative to an independent sampling method was about -10% for determinations near 0.1 ppm and about +7% for determinations in the range of 0.3 to 5.1 ppm. The relative standard deviation at 0.1 ppm was 6.6% and the pooled relative standard deviation for concentrations in the range of 0.3 to 5.1 ppm was 7.7%. Field tests of the method were not as successful.
The ozone concentrations determined with the developed method were much lower than those simultaneously determined with a chemiluminescent monitor and those determined by another iodometric impinger method, the boric acid/ potassium iodide method.
Loss of ozone as a result of reaction with welding fume present in the air samples or as a result of the catalysis of other reactions of ozone by the fume may have contributed to the observed discrepancies.
A tentative personal sampling and analytical method was recommended based on the boric acid/potassium iodide procedure.
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