Hazards in confined space

What makes a confined or enclosed space hazardous Hazards in confined spaces can be separated into two categories physical hazards and atmospheric hazards. 

There are three main hazards of confined spaces. They are oxygen deficiency, toxicity, and flammable and combustible gases, vapors, or dusts. There may be other hazards in confined spaces as well. 

Chemical Reactivity - Reactivity with Water No reaction Reactivity with Common Materials Can catch fire when in contact with porous materials such as wood, asbestos, cloth, soil, or rusty metals Stability During Transport Stable at ordinary temperatures, however when heated this material can decompose to nitrogen and ammonia gases. The decomposition is not generally hazardous unless it occurs in confined spaces Neutralizing Agents for Acids and Caustics Flush with water and neutralize the resulting solution with calcium hypochlorite Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

Special versions are available, such as hazard-proof and for high-pressure operation, but these are not normally applicable to the field of air conditioning. Fans are available with fewer blades (part-solidity) to allow the use of smaller higher-speed motors. There are also fans with short casings having a length little more than that to accommodate the blades for use in confined spaces. 

Recently, there has been much interest in developing water-soluble tributyltin biocides to lessen the costs of application, and to prevent fire hazards when treating material in confined spaces. Bis(tributyltin) oxide itself has a very low aqueous solubility ( 0.001%), but it may be made water-dispersible by the addition of certain (534, 535) quaternary ammonium salts. Formulations of this type, although currently under development as wood preservatives (534), have been used extensively in the United Kingdom for the treatment of stonework to eradicate fungal growths, algae, mosses, and lichens (535). 

Pose flammable or toxic hazards (e.g. by inhalation of ingestion), or affect the eyes, mucous membranes or skin, especially if spillage involves volatile liquids in confined spaces, or if dust can become airborne. 

Liquefied petroleum gas (LPG), stored as a liquid under pressure in cylinders, is widely used in homes as cooking gas. The main hazards associated with LPG are fire or explosion, in the case of even minor leakage. In the case of major leakage in confined spaces, asphyxiation due to deficiency of oxygen also may result. Because LPG is colorless and odorless, a distinctive foul odor is added to enable easy detection of a leak. As LPG vapor is heavier than air, these vapors accumulate at lower levels, and a fire or explosion may result. 

Knowledge of the Hazards. Adequate knowledge of each of the hazards associated with handling hydrogen in any form allows all needed safety practices to be fully implemented. These hazards have been identified as related to flammability, expansion from liquid to gas in confined spaces, improper materials of construction, cold "burns," and breathing atmospheres con-... 

W.F. Marshall, R.W. Hum, Hazard from Engines Rebreathing Exhaust in Confined Space , U.S. Department of die Interior, Bureau of Mines, Report of Investigations 7757, 1973 J6zef Marszalek, Majdanek, the Concentration Camp in Lublin, Interpress, Warsaw 1986... 

Metallic mercury is mostly a problem in confined spaces or where it is handled in industrial processes or in laboratories. It is not generally an environmental problem, more likely an industrial hazard. However, metallic mercury does occur naturally (it was mined in Spain and Slovenia, for example) and the use of mercury for metal reclamation is a potential environmental hazard in countries such as Brazil where miners use it to extract gold from river sediments. Inorganic and organic mercury may be produced from the metallic mercury during its use and subsequent release into the environment. 

Ten per cent of the lower explosive limit (LEL). (Note OSHA considered concentrations in excess of 10% of the LEL to be a hazardous atmosphere in confined spaces.)... 

The growing technology provided experience in coping with the more conventional cryogenic hazards associated with material s brittleness, with cold flesh "burns," and with liquid to gas expansion in confined spaces. 

Pyrotechnically generated smokes from grenades or powder clouds may not be acceptable from a safety point of view in certain circumstances for example, where fires may be produced, or in confined spaces with low rates of ventilation where asphyxial effects could develop. In order to reduce such potential hazards, a variety of approaches have been investigated. One of these is the use of highly volatile PCSI materials, which can be projected into enclosed spaces, but no material of sufficiently low toxicity has yet been found which is acceptable. An alternative approach is the use of a PCSI substance dissolved in a volatile solvent, and the mixture projected into the area by means of a pressurized aerosol canister or a frangible missile. This results in the development of an airborne vapor or aerosol of irritant (Ballantyne, 1979). 

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