In 1979, ferroalloy production was 1.6 Tg (1,830,000 tons), which represents a 21.5% decline since 1971. The number of electric submerged-arc furnaces has also decreased from a total of 158 to 89 for ferroalloys and 7 for calcium carbide. No new furnaces have been built since 1974, and none are subject to the NSPS. Tests made to determine compliance with state regulations showed particulate emission rates in the range of 0.07 to 0.2 kg/MW-h (0.10 to 0.44 lb/MW-h). Fabric filter control systems are widely used on open type furnaces, and high-pressure-drop scrubbers are used on semisealed and closed furnaces. Flares are used to reduce CO emissions. Limited organic emissions data showed a range of 0.15 to 0.29 kg/MW-h (0.33 to 0.63 lb/MW-h) prior to the flare. Because of lack of growth and an absence of new technology, no changes in the NSPS are recommended.