On November 30, 1998, the National Institute for Occupational Safety and Health (NIOSH) received a management request for a health hazard evaluation (HHE) at Lockheed Martin Aeronautical Systems (LMAS) in Marietta, Georgia. The request centered on workers’ exposures to isocyanate-containing compounds during spray painting operations. On February 17-18, 1999, investigators from NIOSH conducted a site visit and exposure assessment for these compounds. At this facility, LMAS manufactures the C-130J Hercules military transport aircraft; and conducts research, development, and limited production of the F-22 Raptor advanced tactical fighter aircraft. Polyurethane paints are used to coat the surfaces of the aircraft and various parts. Air sampling was conducted during polyurethane spray painting operations in paint booths 219 and L-64. Two different isocyanate-containing polyurethane paints were used in these spray painting operations. Both paints were two-component formulations, and were identified by the in-house designations of code 36 and code 46. The code 36 paint contains 40% by weight 1,6-hexamethylene diisocyanate (HDI)-based polyisocyanate, and less than 0.15% HDI. The code 46 paint contains 40% by weight of 4,4'-diphenylmethane diisocyanate (MDI), and 50% MDI-based polyisocyanate. During spray painting, the painters wore a full-face air-purifying respirator with combined particulate and organic vapor cartridges, and a Tyvek suit. The exposure assessment protocol consisted of personal breathing zone (PBZ) air sampling on the painters, and area air sampling around the perimeter of the spray paint booths. The samples were collected to determine short-term, task-based exposures and airborne concentrations to the isocyanate-containing compounds found in the paints. All area air samples were collected using midget impingers containing 15 milliliters of a solution of 1-(9-anthracenylmethyl) piperazine (MAP) in butyl benzoate, followed by a 37 millimeter diameter quartz fiber filter (QFF) impregnated with MAP. PBZ air samples were collected using the MAP-impregnated QFFs. Filter samples were analyzed by high pressure liquid chromatography (HPLC) with ultraviolet and fluorescence detection for both the monomer and polyisocyanate components of the paints. The impinger samples underwent solid-phase extraction, followed by the same analysis used for the filter samples. Monomers were quantified based on comparison of their fluorescence peak heights to those of monomer standards. If detected, poly-isocyanates/oligomers were quantified based on the comparison of their ultraviolet peak areas to those of monomer standards. At the time of the NIOSH survey, two painters were painting parts in booth 219. The painter on the right side of the booth used the code 46 paint, the painter on the left side used the code 36 paint. The MDI and MDI-based polyisocyanate exposure concentrations were 300 and 304 micrograms per cubic meter of air (:g/m3 ) for the right side (code 46) painter. For the left side (code 36) painter, the HDI and HDI-based polyisocyanate exposures were 1.9 and 164 : g/m3 , respectively. Only one painter worked in the L-64 booth. This painter used the code 46 paint, and the MDI exposure was 1364 : g/m3 and the MDI-based polyisocyanate exposure was 1080 : g/m3 . In addition, the total reactive isocyanate group (TRIG) exposures for painters in booth 219 were 206 and 83 : g-NCO/m3 , and the TRIG exposure for the L-64 painter was 831 : g-NCO/m3 . Finally, significant airborne concentrations of the various isocyanate-containing compounds were found by the area air sampling conducted in both spray painting booths. Considering the MDI, MDI-based polyisocyanate, HDI-based polyisocyanate, and TRIG exposure concentrations, the NIOSH investigators conclude that a health hazard exists in the LMAS spray painting booths/operations evaluated during this study. Recommendations are provided to increase the level of protection for workers in the spray painting operations. This includes respiratory protection, protective clothing, medical surveillance, and industrial hygiene surveillance.