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be unhealthy. When the air we breathe Rooms containing CO, systems must loss of strength. CO2 cylinders must there-
<br /> contains 3 — 5 vol.% CO, we experience have effective ventilation. fore be protected from water or aqueous
<br /> headache, respiratory disturbances and Rooms in which large quantities of CO2 fluids (beer, lemonade, etc.).
<br /> discomfort. At 8 — 10 vol.%, cramps, uncon- have collected must be entered only
<br /> sciousness, respiratory arrest, and death with self-contained breathing apparatus. In the filling plant, CO, cylinders must be
<br /> Can occucAt this point the oxygen content This applies even if persons have been checked for water prior to filling, and dried
<br /> of the air is still 19 vol.%, which Is still suf- overcome and urgently require assi- if necessary. But users should also make
<br /> fidenl. The physiologically harmful effect stance. sure that liquids do not enter their Co.
<br /> of these high CO, concentrations therefore If a sudden CO2 emission occurs, give cylinders. One possible safety precaution is
<br /> results not from lack of oxygen, but from priority to Immediate evacuation of low- to Install a backflow preventer.
<br /> the direct effect of carbon dioxide. A maxi- lying areas (pits, basements), where the There is another, very simple safety pre-
<br /> mum workplace concentration (equivalent danger of CO, accumulation is especially caution, which can keep moisture out of t
<br /> to TLV) of 0.5 vol.% has therefore been severe. COI cylinders: they should be emptied only
<br /> defined for CO, Fixed CO, extinguishing systems must be down to a residual pressure of about 5 bar;
<br /> operated, for testing or actual use, only then keep the cylinder valves closed. This
<br /> when no one is present in the threa- prevents molst air from entering Into the
<br /> tened area. If the carbon dioxide can cylinder.
<br /> reach other rooms through ducts, wall
<br /> . `� openings, ventilation, or air-conditioning CO, cylinder valves shall have a overpres-
<br /> systems, these are also considered part sure safety device In the form of a bursting
<br /> of the threatened area. disk that Is secured to the valve with a
<br /> coupling nut, TopreventInadvertent and
<br /> Handling of CO, Cylinders dangerous discharge of CO2, this device
<br /> - - must never be tampered with.
<br /> Important advice for working with any type
<br /> of gas cylinder Is provided In Linde Safety Withdrawing Gas from CO2 Dip Tube
<br /> Caution: Danger or asphyxiation Advice 7 "Safe handling of gas cylinders Cylinders
<br /> and cylinder bundles", and 8 "(Re-) Filling
<br /> Carbon dioxide can also be dangerous to Gases". CO2 dip tube cylinders contain a dip tube
<br /> humans because of cold. When cryogenic which extends from the cylinder valve _
<br /> liquefied Cov or CO2 that has been cooled For CO, cylinders, also note the following: to just above the bottom of the cylinder.
<br /> by expansion, comes in contact with hu- Provided it remains vertical, a dip tube _
<br /> man skin as a spray or snow, it can produce Unauthorised transfer of carbon dioxide cylinder always yields CO2 In liquid form.
<br /> painful "cryogenic burns." Sensitive tissues from one gas cylinder to another con- Note the following particular characterf-
<br /> such as the cornea are particularly at risk. stitutes a safety risk, for the following sties when using these cylinders:
<br /> Large areas of freeze burning can cause reasons: cylinders being filled must meet
<br /> death. (See Linde Safety Advice 1, "Hand- certain requirements so they can reliably
<br /> ling of cryogenic liquefied gases' ) withstand the pressure. In general, only -
<br /> the properly trained personnel of an
<br /> Properties of Dry Ice authorised filling facility can determine
<br /> whether a cylinder is suitable for use. In -
<br /> Dry ice consists of compressed CO, snow addition, it is absolutely mandatory that
<br /> that has been produced by depressurising the contents be monitored and defined
<br /> liquid CO,. At atmospheric pressure the by weighing during filling. According to
<br /> temperature of dry ice is -79"C. when the Pressure Vessel Code, a cylinder may g
<br /> dry ice heats up at atmospheric pressure, contain a maximum of 0,75 kg CO, per litre
<br /> It does not melt but instead evaporates of cylinder volume. This fill factor guaran-
<br /> completely ("sublimes") to form gaseous tees that the pressure in the CO, cylinder CO2 dip tube cylinders are clearly marked
<br /> cabron dioxide hence the name "dry Ice." will not reach the test pressure of 2SO bar as such by the filling plant, The user
<br /> Depending on how much it is compressed, below a temperature of 65°C. If the filling must specifically note that the cylinder Is
<br /> 1 kg of dry ice yields 300 - 400 fires of CO, factor is exceeded, the pressure inside the a CO, dip tube cylinder.
<br /> gas. A considerable pressure build-up can cylinder increases substantially with even • CO2 dip tube cylinders must be used
<br /> therefore occur if dry ice evaporates in a a slight rise in temperature. An overfilled only when the user Intends to withdraw
<br /> gas-tight vessel. CO, cylinder can burst If It is merely expo- liquid carbon dioxide.
<br /> sed to sunlight. it Is highly Inadvisable to • CO2 dip tube cylinders must not be fitted
<br /> 3. Safety Measures transfer carbon dioxide from one cylinder with a regulator, sine the pressure drop
<br /> to another, woul cause the liquid caarbon dioxide to
<br /> Health Precautions solidify into Co. snow, clogging the regu- -
<br /> The pressure in a CO, cylinder depends lator and disabling it.
<br /> inhalation of CO, in concentrated form Is solely on temperature. At 20°C, for exam- CO2 dip tube cylinders must be standing
<br /> dangerous to humans. CO, therefore must ple, It is 57 bar. Even an almost empty CO. upright while gas is being withdrawn, so
<br /> not be present in high concentrations In cylinder remains at 57 bar at 200C, as long that the opening of the dip tube remains
<br /> the air. The following safety precautions as It contains the liquid phase. This means below the CO, liquid level. Thsi is the
<br /> are advisable: that the contents of a Co, cylinder cannot only way In which almost the entire con-
<br /> be determined by measuring its pressure, tents of the cylinder can be withdrawn
<br /> • Keep CO, systems gas-tight. Seal any but only by weighing. in liquid form as Intended.
<br /> leaks immediately. Liquid carbon dioxide emerges from a
<br /> • Any Co. discharge from an operating CO, cylinders are generally made of carbon CO, dip tube cylinder at full cylinder
<br /> facility of a safely valve must be vented steel. This material is corroded by carbonic pressure. The withdrawal device must
<br /> outdoors. acid (CO2 dissolved in H20) a dangerous therefore be appropriately pressure-
<br /> safety Advice.
<br /> ressure-safewndvice. 12 -waking with Urban dioxide co,. Page 2
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