Design and Laboratory Evaluation of a Breath Sampling Respirator for Organic Solvent Biological Monitoring

Abstract

A modified half-face air purifying respirator was developed as a technique for large-scale monitoring that will be acceptable to workers, simple to apply, and relatively sensitive. Exhaled air was directed through the respirator exhaust port and then through a two-part cartridge. The first part contained four layers of activated charcoal cloth which adsorbed organic solvent vapors; the cloth was subsequently desorbed for standard gas chromatographic analysis. The second part contained 70 g of 8–12 mesh molecular sieve whose weight gain was proportional to the volume of air exhaled. The proportionality was determined by independent measurement of volume in subjects while at rest and while exercising. Controlled atmospheres containing toluene at relative humidities near saturation were passed through the cartridge at steady flows equal to resting human ventilatory rates. Toluene recovery was 70 percent for simulated breath concentrations of 0.75 mg/m³ to 60 mg/m³. Nine adult males volunteered to breathe toluene in air at 40 ppm for four hours (TLV = 100 ppm TWA). About 18 hours later, their breath was sampled to simulate a worksite measurement at the start of the next shift. Samples of at least 140 liters were taken from each subject, and the mean exhaled concentration was 344 μg/m³ (0.23% of exposure TWA), in good agreement with literature reports using more complicated methods not appropriate for field application. The device can be used to collect samples of up to 300 liters in 30 minutes, and its sensitivity and selectivity are then limited only by the desorption and analysis of the charcoal adsorbent. The lower limit of quantitation for toluene, with conventional GC analysis, was about 65 μg/m³ (18 ppb). The technique can be applied to most solvents capable of adsorption on charcoal and will permit sampling large numbers of workers with minimal job disruption.