Results of a field study that estimated the service lives of several different brands of organic-vapor respirator cartridges for nitroglycerin are presented. Respirator carbon tubes (RCTs) were used to sample in a workplace where gun powder was manufactured and where nitroglycerin levels varied from approximately 0.1-0.7 mg/m3. Tenax adsorbent tubes were used to monitor for nitroglycerin upstream and downstream of RCTs and were subsequently analyzed by a gas-chromatography method. A series of 10 trials failed to find evidence of nitroglycerin breakthrough. Estimates of the minimum service lives of respirator cartridges varied from 7-81 hours for nitroglycerin levels of 1.0 mg/m3, 10 times the current Occupational Safety and Health Administration Permissible Exposure Level. One trial specifically examined the potential of nitroglycerin to prematurely break through a cartridge due to bed migration, and results failed to indicate this as a potential problem. A field validation of the Tenax adsorbent tube method for nitroglycerin monitoring resulted in an accuracy of +/- 77-88% at the 95% confidence level. An unexpected finding was that up to 10% of the ambient nitroglycerin collected was adsorbed to an aerosol. This finding led to the recommendation that the addition of a prefilter to an organic vapor cartridge may be required when using air-purifying respirators to protect workers from some nitroglycerin exposures.