pling at three locations conducted over 6 h during the missions of two submarines. Sampling indicated concentrations of 2.072-5.476 ppm and of 2.740-3.035 ppm, depending on the collection method, on one submarine, and concentrations of 0.452-3.015 ppm and of 2.092-2.938 ppm, depending on the collection method, on the other submarine. Raymer et al. (1994) reported the results of a similar sampling exercise (two submarines, three locations, and sampling duration of 6 h). Freon 12 concentrations were reported at 4.0 and 1.4 ppm in the fan rooms, 2.0 ppm in the galleys, and 1.8 and 4.0 ppm in the engine rooms.

The toxicity of Freon 12 has been studied in a number of species exposed acutely and repeatedly. Most of those studies, however, were conducted in the 1970s and earlier and lack complete documentation. Some studies, although frequently cited in review articles, are unpublished or were published in foreign journals and were available only in published reviews. The information evaluated indicates that Freon 12 has relatively low acute toxicity by inhalation (for example, LC₅₀s over 500,000 ppm in animals) with weak narcotic and moderate cardiac-sensitizing effects. The EC₅₀s (the concentrations at which a specified effect is observed in 50% of a test population) for cardiac sensitization, the most serious toxic effect, have been reported to be at least 50,000 ppm in dogs and other animals given intravenous epinephrine and over 100,000 ppm in animals