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Safety Advice - I 12 - Working with Carbon dioxide CO2 . p � . . - me In eel, I aa ev leen c — ' � i 1. introduction At atmospheric pressure, CO. Isgaseous. Under certain conditions it is also possible Al temperatures between -56.6 and to withdraw CO, from the cylinder in liquid Working safely with carbon dioxide means +31 .10C, and pressures of at least 5.2 form (see section 3). if liquid CO, is abrupt- understanding the characteristics of this bar, CO, can exist in liquid form. Liquid ly depressurised during withdrawal, It is gas and taking suitable safely precautions. CO, cannot exist at atmospheric pressure intensively cooled, producing a mixture of This Safety Advice Is a recommendation (1 bar). CO, gas and CO2 snow. based on practical experience; it supple- • At temperatures below -56.6°C, 002 can ments, but does not replace, mandatory occur In the solid state. Physiological Effects safety stipulations. • All three physical states are possible I , Carbon dioxide is sometimes referred to as only at the "triple point" (-56,60C, 5.2 As a gas, carbon dioxide is coloolless and "carbonic acid". In this Safety Advice, the bar). essentially odourless and tasteless. It Is term "carbonic acid" is used only to refer therefore practically impossible to detect to an aqueous solution of carbon dioxide These physical states can easily change: with the human senses. (CO2 in H20). In the gas cylinder CO2 is in the liquid state, Carbon dioxide is considered nontoxic. It Is 2. Properties i.e. "under pressure liquefied." The piles- not a hazardous substance as defined by sure In the cylinder is approximately 57 the Dangerous Substances resp. Prepara- Chemical Properties bar at 20°C. When CO. is withdrawn from tions Directive. The air we brethe contains the cylinder through a regulator set at an about 0.03 vol.% carbon dioxide. This Carbon dioxide is non-flammable and, outlet pressure of less than 52 bar, gase- concentration is essential for life, since under atmospheric conditions, chemically ous CO, Is produced: 1 kg of liquid expands It stimulates the respiratory centre and stable and inert, combustion reactions are to about 550 litres of gas at atmospheric controls the volume and rate at which we Inhibited or completely suppressed by CO, pressure. breathe. At higher concentrations, CO2 can I carbon dioxide (an react vigorously with Sales of aggregation depending OnPT55ureand temperature certain substances, such as ammonia or amines. ro.000 Carbon dioxide dissolves In water to pro- duce carbonic acid, which reacts as a weak Mc cctx: y.. acid and has a corrosive effect on carbon steel and a few non-ferrous metals. ....... ?a Physical Properties � � : - As a gas at atmospheric pressure, carbon 10 dioxide is approximately 1 .5 times as hea- .vy as;air. Co. therefore lends to flow down- ward, and can collect in pits, basements, or natural depressions- if there is little air movement, these pools of CO. can persist for many hours. orr The physical states of carbon dioxide, -foo -80 -sD -ao -20 ° 20 ao which depend on pressure and tempera- rempemtur (•g ture, deserve particular attention: Safety Advice. 12 - Working with Carbon dioxide CO, Page 1 l