Hazards of Cold

The major injuries associated with cold conditions are either generalized (affects the whole body) or localized (affects a part of the body). A generalized injury from extremes of cold is hypothermia localized injuries include frostbite and trenchfoot. 

In cold air, the body loses heat principally by radiation from exposed skin surfaces and a small amount of convection or conduction. The rate of heat loss increases with movement of air across the exposed skin, which produces a cooling effect. The heat lost from skin exposed to a 10-mile-per-hour wind when the ambient temperature is 10°F will be the same as that from skin in still air at -9°F. The wind chill factor is an indication of relative heat loss only. Freezing of tissue will not occur unless the temperature is 32°F or lower. For example, the wind chill factor for a 15-mile-per-hour wind at an ambient temperature of 40°F is 22°. Tissue and blood will not freeze, but the body will compensate for the added heat loss. 

Some measures employers can use to protect workers from cold hazards are to install wind shields at some locations, provide heated shelters for warming breaks, provide warm drinks for fluid replacement, and rotate workers frequently. 

Chemical bums, like thermal bums, destroy body tissues, however, chemical bums continue to destroy body tissue until the chemicals are washed away completely. The primary hazardous effects of chemical bums are infection, loss of body fluids, and shock. 

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It is clear, therefore, that both styles of major hazard regulation would have averted the accident, had they been in place. A safety case regime would have mandated a systematic hazard identification procedure which would have identified and controlled the hazard of cold temperature embrittlement. An incident report system which required the reporting and investigation of abnormal temperature events and leaks would also have resulted the discovery and control of the danger of embrittlement. 

The chemistry, and hence hazards, of hot, or radioactive, elements parallels that of their cold isotopes. However, the radiation poses additional toxicity hazards. A qualitative classification of selected isotopes in terms of their toxicity is given in Table 10.2. The biological effects of ionizing radiation stem mainly from damage to individual cells following ionization of the water content. Oxidizing species, e.g. hydrogen peroxide. 

Precautions recommended include use of cold zinc and total enclosure of such processes [2]. The possibility of explosions of zinc dust suspended in air is presented as a serious hazard [3], A serious dust explosion in the air filter unit of a zinc grinding mill was initiated by a spark from an explosion relief panel [4], See Zinc chloride, below... 

The present procedure represents a modification of two previously published procedures,2 3 and results in a safer, more convenient preparation of the title compound. In Step A, the ratio of reagents has been adjusted to allow for the formation of only pentaerythrityl tetrachloride and trichlorohydrin none of the dichlorinated product is produced. Thus work up of the reaction is easier the product can be filtered rather than extracted, so minimal solvent is used, and the crude products are used in Step B, thus avoiding a tedious distillation. Step B has also been modified to make it safer and more convenient. The crude material from Step A is used, and addition of nitric acid over a longer period reduces the hazards of this step. Previously, it was noted that after the nitric acid was added in one portion and the mixture was heated, "a reaction became apparent, whereupon the flask was lowered rapidly into a waiting cold bath and the operator withdrew. 2 Step C is a more detailed modification of the procedure reported by the Russian workers3 as an improvement to the original method of Mooradian and Cloke.2 The latter used quinoline to catalyze the conversion of tris(chloromethyl)acetic acid to 3-chloro-2-(chloromethyl)propene. 

Quenching the vapour with cold air in the chamber may increase the rate of heat removal although excessive nucleation is likely and the product crystals will be very small. Condenser walls may be kept free of solid by using internal scrapers, brushes, and other devices, and all vapour lines in sublimation units should be of large diameter, be adequately insulated, and if necessary, be provided with supplementary heating to minimise blockage due to the buildup of sublimate. One of the main hazards of air-entrainment sublimation is the risk of explosion since many solids that are considered safe in their normal state can form explosive mixtures with air. All electrical equipment should therefore be flame-proof, and all parts of the plant should be efficiently earthed to avoid build-up of static electricity. 

There has been a reluctance to provide water spray on compressors or turbines that typically tend to run "hot," with respect to the risk that a sudden deluge of cold water will result in severe thermal shock and cause cracking of the compressor case. However, studies indicate that this hypothesis is not valid (EPRI, 1985). These studies support the use of water spray protection where the fire hazard so warrants. Water mist systems are now being approved for gas turbines and compressors. 

Excessively low temperature may involve the hazard of brittle fracture. A vessel that is out of use in cold weather could be at a subzero temperature and well below its nil-ductility temperature. In startup, the vessel should be warmed slowly and uniformly until it is above the NDT. A safe value is 38°C (100°F) for plate if the NDT is unknown. The vessel should not be pressurized until this temperature is exceeded. Even after the NDT has been passed, excessively rapid heating or cooling can cause high thermal stresses. 

Cerium, Ce at wt 140.13,at No 58 one of the "rare earth elements gray, ductile, maleable metal which tarnishes in moist air d 6.78 mp 645°, bp 1400° sol in dil acids insol in cold w slowly oxidizes in hot w forms numerous alloys salts. It occurs in monazite sand which is an orthophosphate of thorium and rare earths. Ce-Fe pyrophoric alloys are used as sparking flints for lighters, tracer bullets for military signalling. Ce metal is used as component of some rocket proplnts and in alloys for jet engines. Toxicity, fire expln hazards of Ce are discussed in Ref 5- Ce alloy, called Misch Metal Ce 52, Nd 18, Pr 5, Sm 1 other substances(such as La, Ca, Al, C, Si Fe) 24%, has many applications. Mixt of Ce ... 

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