In the event of an emergency such as facility shutdown during process operation, the by-product gas must be urgently discharged to the vent stack to prevent leakage, fire, and explosion. At this time, the explosion drop value of the released by-product gas is calculated using ISO 10156 formula, which is 27.7 vol%. Therefore, it does not correspond to flammable gas because it is less than 13% of the explosion drop value, which is the standard for flammable gas defined by the Occupational Safety and Health Act, and since the explosion drop value is high, it can be seen that the risk of fire explosion is low even if it is discharged urgently with the vent stock. As a result of calculating the range of explosion hazard sites for hydrogen gas discharged to the Bent Stack according to KS C IEC 60079-10-1, 23 meters were calculated. Since hydrogen is lighter than air, electromechanical devices should not be installed within 23 meters of the upper portion of the Bent Stack, and if it is not possible, an explosion-proof electromechanical device suitable for type 1 of dangerous place should be installed. In addition, the height of the stack should be at least 5 meters so that the diffusion of by-product gas is facilitated in case of emergency discharge, and it should be installed so that there are no obstacles around it.

Carbon black is a material in the form of fine black powder obtained by incomplete combustion or pyrolysis of hydrocarbons, and is composed of 90-99% carbon, and the rest is composed of hydrogen and oxygen. In the event of an emergency during the manufacture of carbon black, the generated tail gas should be safely discharged through an emergency line to prevent fire, explosion, and environmental pollution accidents caused by the tail gas. If the pressure continues to rise, the pressure control valve shall operate and the rupture plate shall be ruptured sequentially and the tail gas shall be discharged to the vent stack through the emergency line. As an emergency emission system, even if some untreated substances in the tail gas are released into the atmosphere, they are lighter than air, so it is safe to discharge them to a safe place through the Vent Stack. If the gas pressure is rising or worse, it is discharged from the Vent Stackine, and discharging fuel.

A 57 years old female complained of severe pain on the right temporomandibular joint (TMJ) area. Her right condyle had been partly resected under surgical operation 13 years ago due to condyle hypertrophy, thereafter she felt dull pain on TMJ area and recently the lesion became severely swelled and painful leading to cancer phobia. The present radiological views showed slightly enlarged and sclerosed condyle with increased radiopacity, but its articular sliding function was almost disable during mouth opening. The patient’s TMJ lesion was carefully managed with conservative physiotherapy and pain treatment. The microsection of condyle head obtained from the previous operation was re-evaluated histologically, and it was finally diagnosed as osteochondrosis dissecans (OCD), exhibiting hyperplastic proliferation of cartilage in condyle head and marked vascular dilatation in epiphyseal zone. This abnormal cartilage tissue was distinguishable from normal cartilage tissue found in the peripheral cartilaginous cap of the same microsection. The involved cartilage cap showed thick hypertrophic chondrocyte zone with horizontal and vertical clefts accompanying diffuse hyaline degeneration. The superficial fibrous zone of cartilage cap was thickened and frequently peeled off, while lower hypertrophic zone of cartilage cap was highly cellular and proliferative. Consequently, the endochondral ossification became aberrant and resulted pre-mature apoptosis of many hypertrophic chondrocytes, followed by diffuse and mild inflammatory reaction in the underlying marrow tissue. Therefore, it was suggested that this hypertrophic condyle lesion, OCD, be differentiated depending on radiological and histological features from ordinary condyle hyperplasia, osteochondroma, and osteoarthritis, and that the pathological confirmation of OCD may provide a reliable modality for dental and medical treatment of chronic and painful TMJ lesion.

Krox-25, a Kruppel type zinc finger protein, may play an important role for the morphogenesis of tooth in ectomesenchymal interaction between enamel epithelium and odontogenic mesenchyme. The interrupted expression of Krox-25 by antisense inhibition is supposed to affect the abnormal development of tooth germ similar to the deranged proliferation of odontogenic tumors. This study was performed to know the histomorphogenetic effect of Krox-25 antisense inhibition in tooth germs of mouse embryos and to understand the abnormal expressions of Krox-25 in different odontogenic tumors which proliferate in aberrant direction of ecto-mesenchymal interaction. Total 95 tooth germs obtained from pregnant mice in the 13th day of fertilization were cultured with antisense oligonucleotides targeting mouse Krox-25 gene, and their histological patterns were compared with those of different odontogenic tumors, i.e., ameloblastic fibro-odontoma (n=5), ameloblastoma (n=8), and ameloblastic carcinoma (n=2). Resultantly, the cultured tooth germs treated with antisense oligodeoxynucleotides produced primitive dentine and enamel by odontoblasts and ameloblasts, respectively, but they aberrantly grew and formed abnormal tooth organs. Especially, the harmonious growth of enamel and dentine formation was greatly deranged by the antisense inhibition in the organ culture system. These findings were much similar to the abnormal growth of odontogenic tumors. The relatively well differentiated enamel epithelium of ameloblastic fibro-odontoma showed irregularly strong reaction of Krox-25, while the poorly differentiated enamel epithelium of ameloblastic carcinoma showed weak reaction. These data suggest that Krox-25 may play important roles for the histomorphogenesis of tooth germ by signaling the ecto-mesenchymal interaction between odontoblasts and ameloblasts in normal tooth germ development of mouse embryos as well as in cytodifferentiation of odontogenic tumors.