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This guideline summarizes pertinent information about carbon monoxide for workers and employers as well as for physicians, industrial hygienists, and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. Recommendations may be superseded by new developments in these fields; readers are therefore advised to regard these recommendations as general guidelines and to determine whether new information is available.
SUBSTANCE IDENTIFICATION * Formula CO * Structure (For Structure, see paper copy) * Synonyms Coal gas, carbon oxide, carbonic oxide, exhaust gas, flue gas * Identifiers
Carbon monoxide is an odorless, colorless gas or, under high pressure, a liquid. CHEMICAL AND PHYSICAL PROPERTIES * Physical data
The National Fire Protection Association has assigned a flammability rating of 4 (severe fire hazard) to carbon monoxide.
Emergency personnel should stay out of low areas and ventilate closed spaces before entering. Vapors may travel to a source of ignition and flash back. Vapors are an explosion and poison hazard indoors, outdoors, or in sewers. Containers of carbon monoxide may explode in the heat of the fire and should be moved from the fire area if it is possible to do so safely. If this is not possible, cool fire-exposed containers from the sides with water until well after the fire is out. Stay away from the ends of containers. Personnel should withdraw immediately if a rising sound from a venting safety device is heard or if there is discoloration of a container due to fire. Firefighters should wear a full set of protective clothing, including a self-contained breathing apparatus, when fighting fires involving carbon monoxide. EXPOSURE LIMITS * OSHA PEL The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for carbon monoxide is 50 parts per million (ppm) parts of air (55 milligrams per cubic meter (mg/m(3))) as an 8-hour time-weighted average (TWA) concentration [29 CFR Table Z-1]. * NIOSH REL The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for carbon monoxide of 35 ppm (40 mg/m(3)) as an 8-hour TWA and 200 ppm (229 mg/m(3)) as a ceiling [NIOSH 1992]. * ACGIH TLV The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned carbon monoxide a threshold limit value (TLV) of 25 ppm (29 mg/m(3)) as a TWA for a normal 8-hour workday and a 40-hour workweek [ACGIH 1994, p. 15]. * Rationale for Limits The NIOSH limit is based on the risk of cardiovascular effects [NIOSH The ACGIH limit is based on the risk of elevated carboxyhemoglobin levels [ACGIH 1991, p. 229].
HEALTH HAZARD INFORMATION * Routes of Exposure Exposure to carbon monoxide can occur through inhalation of the gas and eye or skin contact with the liquid. * Summary of toxicology
* Emergency medical procedures: [NIOSH to supply] Rescue: Remove an incapacitated worker from further exposure and implement appropriate emergency procedures (e.g., those listed on the Material Safety Data Sheet required by OSHA's Hazard Communication Standard [29 CFR 1910.1200]). All workers should be familiar with emergency procedures, the location and proper use of emergency equipment, and methods of protecting themselves during rescue operations. EXPOSURE SOURCES AND CONTROL METHODS The following operations may generate or involve carbon monoxide and lead to worker exposures to this substance: * The manufacture and transportation of carbon monoxide Operations near furnaces, ovens, stoves, forges, and kilns when they are being fired up to operating temperatures; firefighting, particularly in mines; testing of internal combustion engines; operations near portable stoves Use in organic chemical synthesis, particularly in the Fischer-Tropsch process for petroleum products; in fuel gas mixtures for industrial and domestic heating; as a reducing agent in metallurgical processes such as the Mond process for the recovery of nickel; in the manufacture of metal carbonyl catalysts Liberation of exhaust from faulty equipment on autos, buses, airplanes, and boats; use of compressed air in respiratory devices in industry or breathing mixtures in diving, when the air is supplied from reciprocating oil-lubricated compressors Methods that are effective in controlling worker exposures to carbon monoxide, depending on the feasibility of implementation, are as follows: * Process enclosure Local exhaust ventilation General dilution ventilation Personal protective equipment Workers responding to a release or potential release of a hazardous substance must be protected as required by paragraph (q) of OSHA's Hazardous Waste Operations and Emergency Response Standard [29 CFR Good sources of information about control methods are as follows:
Biological monitoring involves sampling and analyzing body tissues or fluids to provide an index of exposure to a toxic substance or metabolite. A readily available biological monitoring method for carbon monoxide involves the measurement of carboxyhemoglobin concentration in the blood by means of automated visible spectrophotometry. The recommended maximum allowable carboxyhemoglobin level for workers is 5 percent, which corresponds to an 8-hour exposure of 35 ppm. Exposure at the current PEL of 50 ppm for 8 hours will yield a carboxyhemoglobin level of 8 to 10 percent in most workers. A pre-exposure sample should be taken and analyzed to determine background carboxyhemoglobin levels resulting from smoking, various diseases, and non-occupational exposures. It is especially important that smokers and non-smokers be measured separately; the carboxyhemoglobin levels in smokers range from 3 to 10 percent and may be as high as 20 percent in cigar smokers. WORKPLACE MONITORING AND MEASUREMENT Neither NIOSH nor OSHA has a recommended method for full-shift sampling ofemployee exposure to carbon monoxide in the workplace. However, the following analytical methods are available. Determination of a worker's exposure to airborne carbon monoxide is made using an Ecolyzer direct reading field instrument. This instrument is capable of detecting carbon monoxide concentrations between 0 and 600 ppm. Several types of detector tubes are available to screen for the presenceof carbon monoxide; these tubes have a reported limit of detection of 0.5 ppm. This equipment and the ranges of carbon monoxide detection are described in the OSHA Computerized Information System [OSHA 1994].
PERSONAL HYGIENE PROCEDURES If liquid carbon monoxide contacts the skin, workers should flush the affected areas immediately with tepid water, followed by washing with soap and water. Clothing contaminated with liquid carbon monoxide should be removed immediately. Workers should not eat, drink, use tobacco products, apply cosmetics, ortake medication in areas where liquid carbon monoxide is handled,processed, or stored. STORAGE Liquid carbon monoxide should be stored in a cool, dry, well-ventilated area in tightly sealed containers that are labeled in accordance with OSHA's Hazard Communication Standard [29 CFR 1910.1200]. Containers of carbon monoxide should be protected from physical damage and should be stored separately from strong oxidizing agents and halogenated compounds. SPILLS AND LEAKS In the event of a spill or leak involving carbon monoxide, persons not wearing protective equipment and clothing should be restricted from contaminated areas until cleanup has been completed. The following steps should be undertaken following a spill or leak:
U.S. Environmental Protection Agency (EPA) requirements for emergency planning, reportable quantities of hazardous releases, community right-to-know, and hazardous waste management may change over time. Users are therefore advised to determine periodically whether new information is available. * Emergency planning requirements Carbon monoxide is not subject to EPA emergency planning requirements under the Superfund Amendments and Reauthorization Act (SARA) (III) in USC 11022. * Reportable quantity requirements for hazardous releases Employers are not required by the emergency release notification provisions in 40 CFR Part 355.40 to notify the National Response Center of an accidental release of carbon monoxide; there is no reportable quantity for this substance. * Community right-to-know requirements Employers are not required by EPA in 40 CFR Part 372.30 to submit a Toxic Chemical Release Inventory form (Form R) to EPA reporting the amount of carbon monoxide emitted or released from their facility annually. * Hazardous waste management requirements EPA considers a waste to be hazardous if it exhibits any of the following characteristics: ignitability, corrosivity, reactivity, or toxicity as defined in 40 CFR 261.21-261.24. Under the Resource Conservation and Recovery Act (RCRA) [40 USC 6901 et seq.], EPA has specifically listed many chemical wastes as hazardous. Although carbon monoxide is not specifically listed as a hazardous waste under RCRA, EPA requires employers to treat waste as hazardous if it exhibits any of the characteristics discussed above. Providing detailed information about the removal and disposal of specific chemicals is beyond the scope of this guideline. The U.S. Department of Transportation, EPA, and State and local regulations should be followed to ensure that removal, transport, and disposal of this substance are conducted in accordance with existing regulations. To be certain that chemical waste disposal meets EPA regulatory requirements, employers should address any questions to the RCRA hotline at (703) 412-9810 (in the Washington, D.C. area) or toll-free at (800) 424-9346 (outside Washington, D.C.). In addition, relevant State and local authorities should be contacted for information on any requirements they may have for the waste removal and disposal of this substance. RESPIRATORY PROTECTION * Conditions for respirator use Good industrial hygiene practice requires that engineering controls be used where feasible to reduce workplace concentrations of hazardous materials to the prescribed exposure limit. However, some situations may require the use of respirators to control exposure. Respirators must be worn if the ambient concentration of carbon monoxide exceeds prescribed exposure limits. Respirators may be used (1) before engineering controls have been installed, (2) during work operations such as maintenance or repair activities that involve unknown exposures, (3) during operations that require entry into tanks or closed vessels, and (4) during emergencies. Workers should only use respirators that have been approved by NIOSH and the Mine Safety and Health Administration (MSHA). * Respiratory protection program Employers should institute a complete respiratory protection program that, at a minimum, complies with the requirements of OSHA's Respiratory Protection Standard [29 CFR 1910.134]. Such a program must include respirator selection, an evaluation of the worker's ability to perform the work while wearing a respirator, the regular training of personnel, respirator fit testing, periodic workplace monitoring, and regular respirator maintenance, inspection, and cleaning. The implementation of an adequate respiratory protection program (including selection of the correct respirator) requires that a knowledgeable person be in charge of the program and that the program be evaluated regularly. For additional information on the selection and use of respirators and on the medical screening of respirator users, consult the latest edition of the NIOSH Respirator Decision Logic [NIOSH 1987b] and the NIOSH Guide to Industrial Respiratory Protection [NIOSH 1987a]. PERSONAL PROTECTIVE EQUIPMENT Workers should use appropriate personal protective clothing and equipmentthat must be carefully selected, used, and maintained to be effective inpreventing skin contact with liquid carbon monoxide. The selection of theappropriate personal protective equipment (PPE) (e.g., gloves, sleeves, encapsulating suits) should be based on the extent of the worker's potential exposure to liquid carbon monoxide. To evaluate the use of protective materials with liquid carbon monoxide, users should consult the best available performance data and manufacturer's recommendations. Significant differences have been demonstrated in the chemical resistance of generically similar PPE materials (e.g., butyl) produced by different manufacturers. In addition, the chemical resistance of a mixture may be significantly different from that of any of its neat components. Any chemical-resistant clothing that is used should be periodically evaluated to determine its effectiveness in preventing dermal contact. Safety showers and eye wash stations should be located close to operations that involve liquid carbon monoxide. Splash-proof chemical safety goggles or face shields (20 to 30 cm long, minimum) should be worn during any operation in which a solvent, caustic, or other toxic substance may be splashed into the eyes. In addition to the possible need for wearing protective outer apparel e.g., aprons, encapsulating suits), workers should wear work uniforms, coveralls, or similar full-body coverings that are laundered each day. Employers should provide lockers or other closed areas to store work and street clothing separately. Employers should collect work clothing at the end of each work shift and provide for its laundering. Laundry personnel should be informed about the potential hazards of handling contaminated clothing and instructed about measures to minimize their health risk. Protective clothing should be kept free of oil and grease and should be inspected and maintained regularly to preserve its effectiveness. Protective clothing may interfere with the body's heat dissipation,especially during hot weather or during work in hot or poorly ventilated work environments.
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