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Home , Carbon monoxide, NFPA 704, Reducing agent, Temperature

Safetygram 19

Carbon

Carbon monoxide is a colorless, odorless, flammable, toxic . High-purity that is dry and free of compounds is normally noncorrosive to at atmospheric . Lower-purity grades containing moisture, sulfur compounds and other impurities can form toxic carbonyls and can cause cracking in carbon steels at elevated . Chemically, carbon monoxide is stable but can act as a strong at elevated temperatures.

Several different grades of carbon monoxide are available to support various applications. These grades range in purity from commercial grade at 98.0% to research grade at 99.99%.

Applications Carbon monoxide is used widely by the chemical industry in the production of inorganic chemicals (metal carbonyls, dioxide), organic chemicals ( and citric ), and chemical intermediates (toluene and diiso- , used to produce polyurethane). Carbon monoxide in combination with several other (, , and ) provides a gas, called , which is used as a substitute for . It is also used as a reducing agent in metals refining. sometimes incorporate limited of carbon monoxide in meat, poultry and fish to maintain wholesomeness and provide flexibility in distribution.

Manufacture Most carbon monoxide is manufactured by reforming natural gas. Other methods of manufacture include incomplete of carbonaceous ma- terials, dehydration of with , reduction of carbon diox- ide over hot and by reacting carbon and at elevated temperatures.

Safety considerations Toxicity Carbon monoxide is toxic; the risk of exposure is increased because carbon monoxide is odorless. Carbon monoxide is a chemical asphyxiant which com- bines chemically with in to inhibit the transfer of oxygen through the . The affinity of carbon monoxide for hemo- globin is approximately 200 that of oxygen. Because carbon monoxide combines preferentially with hemoglobin to the exclusion of oxygen, oxygen cannot be transported to tissues and organs, resulting in oxygen starvation. This strong affinity of carbon monoxide for hemoglobin means that small amounts of the gas may pose serious problems. The carbon monoxide-hemoglobin bond is reversible, and the gas is gradually released if uncontaminated air is breathed. Carbon monoxide is colorless, taste- Table 1: Carbon Monoxide Physical and Chemical Properties less, odorless, and is detectable only CO by specific techniques or instrumenta- Molecular 28.01 tion. For these reasons, special precau- point @ 1 atm –312.7˚F –191.5˚C tions are required when hazardous point @ 1 atm –337.2˚F –205.1˚C concentrations are possible. Critical temperature –220.4˚F –140.2˚C Flammability Critical pressure 507.5 psig 3499 kPa, abs When mixed with air, carbon monox- Gas @ 70˚F (21.1˚C), 1 atm 0.075 lb/ft3 0.0012 g/cm3 ide poses an immediate . Specific gravity (air = 1) 0.9676 Carbon monoxide has a very broad Specific @ 70˚F (21.1˚C), 1 atm 13.8 ft3/lb 0.862 m3/kg flammability range. The flammable Flammability limits 12.5% vol LFL 74% vol UFL range, sometimes referred to as the range, is the range of in air that will burn or Pressure explode if ignition is intro- Carbon monoxide is shipped as a com- duced. The limiting concentrations for pressed gas at pressures up to 2000 the range are the Lower Flammable psig. Pressure is stored energy and Limit (LFL) and the Upper Flammable must be handled correctly to prevent Limit (UFL). Any concentration be- uncontrolled releases. A compressed tween the LFL and the UFL will burn containing pressure or explode if an ignition source is can be propelled at of greater introduced. Concentrations below the than 35 miles an hour if the LFL are too lean to burn, while those is accidentally sheared. Unsecured above the UFL are too rich to burn. pressurized lines can also cause dam- However, concentrations above the age if uncontrolled pressure releases UFL should not be considered safe, occur. Treat all pressurized contain- because they will dilute at the inter- ers and equipment with respect face with the and pass and never perform maintenance or through the flammable range. on pressurized equipment. See Safetygram-14, “Don’t Turn a Cylinder Lower (LFL): Into a Rocket,” for more information. 12.5%

Upper Flammability Limit (UFL): 74.2%

Autoignition Temperature: 1148˚F (620˚C).

2 Containers Table 2: Exposure Limits Carbon monoxide is shipped and ACGIH 8-hour Weighted Average (TWA) 25 ppm stored in high-pressure cylinders, tube NIOSH Recommended Exposure Limit (REL) 35 ppm trailers or ISO modules, depending on OSHA Permissible Exposure Limit (PEL) 50 ppm the quantity required by the consum- NIOSH Immediately Dangerous to and Health (IDLH) 1200 ppm er. These containers are manufactured Lethal Concentration 50% of test subjects die (LC50) 1807 ppm (0.18%) according to applicable codes and (4 hr, rat), 3760 ppm specifications for the temperatures (0.38%) (1 hr rat) and pressures involved. Lethal Concentration lowest concentration for death (LCl0) 5000 ppm (0.50%), 5 minutes, human Cylinders A typical steel cylinder is a hollow tube with a closed concave that Table 3: Symptoms permits the cylinder to stand upright. Aluminum cylinders have flat bases. CO Concentration Time of Exposure Symptoms (ppm) The opposite end is tapered to a small opening that is threaded to accom- 25 8 hours TWA maximum exposure allowed in workplace modate the installation of a valve. A 50 Typical bloodstream level for a 1 pack a day threaded neck ring is attached to the smoker tapered end to allow a protective cyl- 200 2–3 hours Mild headache, , nausea, and inder valve cap to be installed. Carbon dizziness steel and aluminum are the primary 400 1–2 hours Serious headache, other symptoms materials of construction for carbon intensify, life threatening after 3 hours monoxide. Aluminum is the preferred 800 45 minutes Dizziness, nausea, convulsions, unconscious material because it eliminates the within 2 hours, death within 2–3 hours possibility of pentacarbonyl for- 1600 (0.16%) 20 minutes Headache, dizziness, nausea, death within mation and stress corrosion cracking. 1 hour Cylinders are sometimes manifolded 3200 (0.32%) 5–10 minutes Headache, dizziness, nausea, death within together in a pack or bank to provide 1 hour larger volumes while minimizing 6200 (0.62%) 1–2 minutes Headache, dizziness, nausea, death within cylinder changes. See Safetygram-10, 30 minutes “Handling, Storage, and Use of 12,800 (1.28%) 1–3 minutes Death Compressed Gas Cylinders,” for more information about cylinders.

3 Tube trailers, ISO modules, and Figure 1: Typical Carbon Monoxide Tube Trailer ground storage tubes If large amounts of product are re- quired, carbon monoxide can be sup- plied in tube trailers or ISO modules. The most common configurations for these units are in eight tube bundles of 12 meter (40 ft) by 56 cm (22 in) diameter tubes. These units carry as much as 820 kg (1800 lb) of carbon monoxide. Figure 1 shows a typical carbon monoxide tube trailer. Some applications will require larger quan- tities than are practical to be delivered in cylinder quantities but do not have the room or the space requirements for tube trailers or ISO tube modules. Ground storage tubes may be used to satisfy these applications. Ground tubes can be sized to various volumes to meet specific needs. Ground tubes are similar to the tubes used in tube trailers and ISO modules but are permanently mounted at the site. See Figure 2. They can be sized and mani- Figure 2: Typical Ground Tube Installation folded together to meet a customer’s volume requirements while fitting within their space limitations.

Valves, connections, and pressure relief devices Carbon monoxide containers are sup- plied with a variety of valves, depend- ing upon the grade and application of the product. Each cylinder valve has its own specific operating require- ments. These include the correct way to open and close the valve. Please see Air Products’ Safetygram-23, “Cylinder Valves,” for identifying features, detailed operating instruc- tions, strengths and weaknesses, and cut-away drawings. If you are not sure which valve is on your container, con- tact your supplier for verification.

4 Commercial grade carbon Electronic grade carbon monoxide Valve connections monoxide (typically >98.0% purity) (typically >99.9% purity) Valve outlet connections are designed Commercial grade is typically Electronic Grade product is usually to promote ease of connection to equipped with pressure-seal (back- equipped with a metal diaphragm high-pressure cylinder valves. Various seating) valves. The pressure seal valve valve. Air Products uses three different regional regulatory organizations is a handwheel-operated valve using styles of diaphragm valves in carbon have developed standards for these a two-piece valve stem. Air Products monoxide service: springloaded dia- connections to create continuity recommends pressure seal valves be phragm, tied diaphragm and pneu- amongst the manufacturers. Table 4 used in the fully open or back-seated matic tied diaphragm. The diaphragm shows the specific connections used position. Opening the valve fully valve utilizes a two-piece stem sepa- for carbon monoxide in several causes the lower stem to ride upward rated by non-perforated diaphragms. regions of the world. on its threads until it physically con- These diaphragms prevent leakage tacts the upper stem and mechani- along the valve stem. The springloaded For a more detailed explanation of cally drives the upper stem’s seal ridge diaphragm valve encases the lower how cylinder valve connections into the packing ring. This improves stem in a spring, which the work, recommended closing torques, the seal around the valve stem and stem away from the seat when the and cut-away diagrams, refer to helps to prevent at the top of valve is opened. The tied diaphragm Air Products’ Safetygram-31, “Cylinder the valve. If the valve was back-seated valve utilizes a two-piece stem con- Valve Connections.” using substantial effort, it is possible nected through the diaphragms. Cylinder valve pressure relief that the operator could think the valve The lower stem is physically pulled devices is closed, when in fact it is fully open. away from the seat instead of being Regulations in some regions of the Operators must be trained to use pres- lifted away by the spring. The tied world do not allow the use of pressure sure readings or an equally reliable diaphragm is available in a pneumatic relief devices on high-pressure cylin- indicator to ensure the cylinder valve version for remote operation. ders. In other regions, such as North is closed or open. Close the cylinder America, pressure relief devices are valve tightly using a gloved hand. required by the regulations. When a Air Products recommends always pressure relief device is required on a wearing gloves when operating cyl- high-pressure cylinder containing car- inder valves. NEVER use wrenches or bon monoxide, a combination device other persuaders to operate the valve. consisting of a frangible disk (rated at not more than 1.67 times the working pressure of the cylinder) with a fus- ible backing on the atmospheric side of the disk is required. These pressure relief devices are designed to function in times of fire, as the fusible alloy must melt out before the disk can function. For more informa- tion on pressure relief devices, refer to Safetygram-15, “Cylinder Pressure Relief Devices.”

Table 4: Connections Used for Carbon Monoxide Type of France Germany Japan United Kingdom Connection NF-E 29-650 DIN 477 JIS-B-8246 BS 341 CGA-V-1 Threaded E 5 A(W22L) 4 350 Ultra High Integrity (DISS) has been adopted as an international ISO Standard 724 Caution: The typical gasket used in the 724 connection is made of . If this connection is used, the nickel gasket must be replaced with a or PCTFE gasket.

5 Storage and handling Figure 3: The NFPA 704 Diamond Disposal Always store and handle cylinders for Carbon Monoxide Return unused product to the sup- containing compressed gases in ac- plier. If product must be disposed of cordance with international or local on-site, incineration using a suitable regulations, such as ISO 11625, “ is typically used. Disposal of Cylinders-Safe Handling.” For more carbon monoxide must be done in an information, refer to Air Products’ environmentally acceptable man- Safetygram-10, “Handling, Storage, and ner in compliance with all applicable Use of Compressed Gas Cylinders.” national and local codes. Personnel must know and understand the properties, proper uses, and safety System design and precautions for the specific product maintenance before using the product or associated Materials of construction equipment. Steel and other common metals are satisfactory when handling sulfur- Storage and “EMPTY” tags is highly recom- free, dry carbon monoxide. Iron and Cylinders should be secured in an mended. Storage areas must be posted nickel, present in steel or other metal upright position and stored in a well- with the proper signage, such as “No alloys, can react with carbon mon- ventilated area protected from the ,” “No Open ” or NFPA at high pressure, especially . All precautions necessary for 704 ratings. when and/or sulfur impuri- the safe handling of flammable gas Handling and use ties are present. The carbonyls that must be observed with carbon mon- Use only in well-ventilated areas. may be formed from this reaction are oxide. Avoid storing with oxidizers or If cylinders must be placed indoors, extremely toxic. In addition to the other flammable materials. Carbon they should be in ventilated cabinets formation of carbonyls, corrosion monoxide detectors with audible and or hoods. Use a suitable handcart and/or stress corrosion cracking of visual alarms are highly recommend- designed for cylinder movement. Do iron and nickel alloys is possible, ed for protection of personnel. The not drag, roll or slide cylinders. Never even at low pressures. Systems used storage area should be secure with lim- attempt to lift a cylinder by its cap. in high-pressure carbon monoxide ited access. Storage area temperatures Secure cylinders at all times during service are sometimes -lined to should not exceed 52˚C (125˚F), should storage and transport, and use an provide corrosion resistance. Highly be free from combustible materi- adjustable strap wrench to remove alloyed chrome steels are resistant als and should be free from ignition overly tight cylinder caps. Never insert to these reactions, but it is suggested sources. Storage should be away from anything into the cap holes to as- that users perform stress corrosion heavily traveled areas and emergency sist in cap removal. Ensure that the testing of materials of construction to exits. Avoid areas where salt or other cylinder valve is properly closed, the ensure they will be compatible with corrosive materials are present. valve outlet seal has been reinstalled the high-pressure use of carbon mon- Valve protection caps and valve outlet -tight, and the valve protection oxide under actual conditions. seals must remain on any uncon- cap is installed before returning nected cylinder. When returning a to storage, moving or shipping the cylinder to storage, the valve outlet cylinder. When performing operations seal must be installed leak-tight and such as connection and disconnection the cylinder cap secured. Separate full involving toxic gases, it is advisable and empty cylinders. Avoid excessive to use two people so one can act as a inventory and extended storage time. safety backup. Visually inspect stored cylinders on a routine basis, at least weekly, for any indication of leakage or other prob- lems. Use a first-in, first-out inventory system and keep inventory records up to date. The use of “FULL,” “IN USE,”

6 Buildings Identification number Buildings where carbon monoxide is and eye contact UN1016 used should be adequately ventilated. Carbon monoxide does not attack the Shipping labels Where large quantities are used, me- eyes or skin in itself. However, in the Gas, Flammable Gas (Outside chanical ventilation is recommended. event of a fire, treatment for burns the US) Hazard, Flammable When designing the ventilation sys- may be necessary. Gas (Inside the US) Poison Gas, tems, keep in mind that carbon mon- Inhalation Hazard, Flammable Gas oxide is slightly lighter than air and Ingestion (International going to or from the US) may rise in the event of a leak. Toxic This is not a likely route for exposure. and/or flammable concentrations Inhalation Placard may pocket near ceilings. Electrical Avoid hazardous exposure of rescue Poison Gas lines and equipment must comply personnel. Safely remove victim with national and local building codes List of related Safetygrams to fresh air as quickly as possible. and with electrical codes for Class 1 referenced in text: Trained personnel should administer hazardous areas. Safetygram-10: “Handling, Storage and supplemental oxygen and/or cardio- Use of Compressed Gas Cylinders” Monitoring pulmonary resuscitation, if necessary. Carbon monoxide is colorless, - Seek medical attention promptly. Safetygram-15: “Cylinder Pressure less, tasteless and nonirritating; Keep victim warm. Relief Devices” the gas has no warning properties Safetygram-23: “Cylinder Valves” that can be detected by the human Firefighting Safetygram-31: “Cylinder Valve body. Because of this, monitoring The preferred method for fighting a Connections” is extremely important to identify fuel or flammable gas fire is to shut potentially unsafe concentrations. off the supply of gas, if it can be done This could include personal badges, safely, and allow the gas to burn until Figure 3: Transportation Labels handheld monitors or , room completely consumed. Potential monitors and environmental moni- exist if a carbon monoxide tors. In many cases, it is advisable that fire is extinguished without stopping monitors be tied in to an automatic the flow of gas because of potential shutoff system. exposure of personnel to the toxic gas and the risk of reignition or explo- Personal protective sion. In the meantime, protect the surrounding area and equipment equipment (PPE) from becoming involved. Water spray, (minimum requirements) carbon dioxide, dry chemical or foam General cylinder handling extinguishing agents are effective Safety glasses with side shields, against involving carbon monox- leather gloves and safety shoes. ide. When fighting a carbon monoxide fire, positive pressure, self-contained System operations apparatus should be used In addition to safety glasses with side for personnel protection. shields, leather gloves, and safety shoes: natural fiber clothing like Transportation cotton should be worn and retardant clothing such as Nomex can information provide additional protection from Shipping name fire. Carbon Monoxide, Compressed, 2.3 (2.1), UN1016, Poison–Inhalation Emergency operations Hazard, Zone D Self-contained breathing apparatus and total body covering with flame- Hazard class resistant material such as Nomex. 2.3 (Poison Gas)

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