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Carbon monoxide poisoning

Peter F Clardy, MD
Scott Manaker, MD, PhD
Holly Perry, MD
Section Editors
Stephen J Traub, MD
Michele M Burns, MD, MPH
Deputy Editor
Jonathan Grayzel, MD, FAAEM


Carbon monoxide (CO) is an odorless, tasteless, colorless, nonirritating gas formed by hydrocarbon combustion. The atmospheric concentration of CO is generally below 0.001 percent, but it may be higher in urban areas or enclosed environments. CO binds to hemoglobin with much greater affinity than oxygen, forming carboxyhemoglobin (COHb) and resulting in impaired oxygen transport and utilization. CO can also precipitate an inflammatory cascade that results in CNS lipid peroxidation and delayed neurologic sequelae.

CO poisoning will be reviewed here. A summary table to facilitate emergent management is provided (table 1). Related topics including smoke inhalation and hyperbaric oxygen therapy are presented separately. (See "Hyperbaric oxygen therapy" and "Inhalation injury from heat, smoke, or chemical irritants".)


Fire-related smoke inhalation is responsible for most cases of carbon monoxide (CO) poisoning. Non-fire related CO poisoning is responsible for up to 50,000 emergency department (ED) visits and 1200 deaths per year, making it one of the leading causes of poisoning death in the United States [1-5]. Inadvertent, non-fire related CO poisoning likely causes around 400 deaths annually, while the number of intentional CO poisonings resulting in death is twice as high [1,4,6,7]. The case-fatality rate for non-fire CO poisoning ranges widely, but analysis of aggregated national data from the United States support an overall mortality of 1 to 3 percent [3,4,8,9]. The mortality rate is higher for intentional poisoning than for inadvertent exposure [4].

Unlike intentional poisoning, unintended poisoning demonstrates both seasonal and regional variation, and it is most common during the winter months in cold climates [7]. Morbidity, which is primarily related to late neurocognitive impairment, persists beyond initial stabilization in up to 40 percent of victims [3,8].

Potential sources of CO, other than fires, include poorly functioning heating systems, improperly vented fuel-burning devices (eg, kerosene heaters, charcoal grills, camping stoves [10], gasoline-powered electrical generators [11,12]), and motor vehicles operating in poorly ventilated areas (eg, ice rinks, warehouses, parking garages). CO poisonings following open air exposure to motorboat exhaust have also been reported [13]. In addition, underground electrical cable fires produce large amounts of CO, which can seep into adjacent buildings and homes [14]. An increase in carbon monoxide exposures has been reported to occur in the immediate aftermath of hurricanes [11,15,16].


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Literature review current through: Jul 2017. | This topic last updated: Feb 23, 2017.
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  1. Ernst A, Zibrak JD. Carbon monoxide poisoning. N Engl J Med 1998; 339:1603.
  2. Weaver LK. Carbon monoxide poisoning. Crit Care Clin 1999; 15:297.
  3. Tibbles PM, Perrotta PL. Treatment of carbon monoxide poisoning: a critical review of human outcome studies comparing normobaric oxygen with hyperbaric oxygen. Ann Emerg Med 1994; 24:269.
  4. Hampson NB. U.S. Mortality Due to Carbon Monoxide Poisoning, 1999-2014. Accidental and Intentional Deaths. Ann Am Thorac Soc 2016; 13:1768.
  5. Rose JJ, Wang L, Xu Q, et al. Carbon Monoxide Poisoning: Pathogenesis, Management, and Future Directions of Therapy. Am J Respir Crit Care Med 2017; 195:596.
  6. www.cdc.gov/nceh/airpollution/carbonmonoxide/cofaq.htm (Accessed on August 09, 2005).
  7. Centers for Disease Control and Prevention (CDC). Unintentional non-fire-related carbon monoxide exposures--United States, 2001-2003. MMWR Morb Mortal Wkly Rep 2005; 54:36.
  8. Hardy KR, Thom SR. Pathophysiology and treatment of carbon monoxide poisoning. J Toxicol Clin Toxicol 1994; 32:613.
  9. Hampson NB, Hauff NM. Risk factors for short-term mortality from carbon monoxide poisoning treated with hyperbaric oxygen. Crit Care Med 2008; 36:2523.
  10. Thomassen Ø, Brattebø G, Rostrup M. Carbon monoxide poisoning while using a small cooking stove in a tent. Am J Emerg Med 2004; 22:204.
  11. Centers for Disease Control and Prevention (CDC). Carbon monoxide poisoning from hurricane-associated use of portable generators--Florida, 2004. MMWR Morb Mortal Wkly Rep 2005; 54:697.
  12. Hampson NB, Dunn SL. Carbon Monoxide Poisoning from Portable Electrical Generators. J Emerg Med 2015; 49:125.
  13. Centers for Disease Control and Prevention (CDC). Carbon monoxide poisonings resulting from open air exposures to operating motorboats--Lake Havasu City, Arizona, 2003. MMWR Morb Mortal Wkly Rep 2004; 53:314.
  14. Centers for Disease Control and Prevention (CDC). Carbon monoxide releases and poisonings attributed to underground utility cable fires--New York, January 2000-June 2004. MMWR Morb Mortal Wkly Rep 2004; 53:920.
  15. Centers for Disease Control and Prevention (CDC). Monitoring poison control center data to detect health hazards during hurricane season--Florida, 2003-2005. MMWR Morb Mortal Wkly Rep 2006; 55:426.
  16. Cukor J, Restuccia M. Carbon monoxide poisoning during natural disasters: the Hurricane Rita experience. J Emerg Med 2007; 33:261.
  17. Chang YL, Yang CC, Deng JF, et al. Diverse manifestations of oral methylene chloride poisoning: report of 6 cases. J Toxicol Clin Toxicol 1999; 37:497.
  18. Amsel J, Soden KJ, Sielken RL Jr, Valdez-Flora C. Observed versus predicted carboxyhemoglobin levels in cellulose triacetate workers exposed to methylene chloride. Am J Ind Med 2001; 40:180.
  19. Yasuda H, Yamaya M, Nakayama K, et al. Increased arterial carboxyhemoglobin concentrations in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 2005; 171:1246.
  20. Vogel SN, Sultan TR, Ten Eyck RP. Cyanide poisoning. Clin Toxicol 1981; 18:367.
  21. Tritapepe L, Macchiarelli G, Rocco M, et al. Functional and ultrastructural evidence of myocardial stunning after acute carbon monoxide poisoning. Crit Care Med 1998; 26:797.
  22. Ellenhorn's Medical Toxicology: Diagnosis and Treatment of Human Poisoning, 2nd ed, Ellenhorn MJ, Schonwald S, Ordog G, Wasserberger J (Eds), Williams & Wilkins, Baltimore 1997.
  23. Norris JC, Moore SJ, Hume AS. Synergistic lethality induced by the combination of carbon monoxide and cyanide. Toxicology 1986; 40:121.
  24. Thom SR, Bhopale VM, Fisher D, et al. Delayed neuropathology after carbon monoxide poisoning is immune-mediated. Proc Natl Acad Sci U S A 2004; 101:13660.
  25. Goldbaum LR, Ramirez RG, Absalon KB. What is the mechanism of carbon monoxide toxicity? Aviat Space Environ Med 1975; 46:1289.
  26. Zhang J, Piantadosi CA. Mitochondrial oxidative stress after carbon monoxide hypoxia in the rat brain. J Clin Invest 1992; 90:1193.
  27. Thom SR. Carbon monoxide-mediated brain lipid peroxidation in the rat. J Appl Physiol (1985) 1990; 68:997.
  28. Thom SR, Xu YA, Ischiropoulos H. Vascular endothelial cells generate peroxynitrite in response to carbon monoxide exposure. Chem Res Toxicol 1997; 10:1023.
  29. Tomaszewski C. Carbon monoxide poisoning. Early awareness and intervention can save lives. Postgrad Med 1999; 105:39.
  30. Harper A, Croft-Baker J. Carbon monoxide poisoning: undetected by both patients and their doctors. Age Ageing 2004; 33:105.
  31. Kao LW, Nañagas KA. Carbon monoxide poisoning. Emerg Med Clin North Am 2004; 22:985.
  32. Satran D, Henry CR, Adkinson C, et al. Cardiovascular manifestations of moderate to severe carbon monoxide poisoning. J Am Coll Cardiol 2005; 45:1513.
  33. Henry CR, Satran D, Lindgren B, et al. Myocardial injury and long-term mortality following moderate to severe carbon monoxide poisoning. JAMA 2006; 295:398.
  34. Thom SR, Taber RL, Mendiguren II, et al. Delayed neuropsychologic sequelae after carbon monoxide poisoning: prevention by treatment with hyperbaric oxygen. Ann Emerg Med 1995; 25:474.
  35. Choi IS. Delayed neurologic sequelae in carbon monoxide intoxication. Arch Neurol 1983; 40:433.
  36. Kwon OY, Chung SP, Ha YR, et al. Delayed postanoxic encephalopathy after carbon monoxide poisoning. Emerg Med J 2004; 21:250.
  37. Hampson NB, Little CE. Hyperbaric treatment of patients with carbon monoxide poisoning in the United States. Undersea Hyperb Med 2005; 32:21.
  38. Seger D, Welch L. Carbon monoxide controversies: neuropsychologic testing, mechanism of toxicity, and hyperbaric oxygen. Ann Emerg Med 1994; 24:242.
  39. Bozeman WP, Myers RA, Barish RA. Confirmation of the pulse oximetry gap in carbon monoxide poisoning. Ann Emerg Med 1997; 30:608.
  40. Tremper KK, Barker SJ. Pulse oximetry. Anesthesiology 1989; 70:98.
  41. Barker SJ, Curry J, Redford D, Morgan S. Measurement of carboxyhemoglobin and methemoglobin by pulse oximetry: a human volunteer study. Anesthesiology 2006; 105:892.
  42. Roth D, Herkner H, Schreiber W, et al. Accuracy of noninvasive multiwave pulse oximetry compared with carboxyhemoglobin from blood gas analysis in unselected emergency department patients. Ann Emerg Med 2011; 58:74.
  43. American College of Emergency Physicians Clinical Policies Subcommittee (Writing Committee) on Carbon Monoxide Poisoning:, Wolf SJ, Maloney GE, et al. Clinical Policy: Critical Issues in the Evaluation and Management of Adult Patients Presenting to the Emergency Department With Acute Carbon Monoxide Poisoning. Ann Emerg Med 2017; 69:98.
  44. Touger M, Gallagher EJ, Tyrell J. Relationship between venous and arterial carboxyhemoglobin levels in patients with suspected carbon monoxide poisoning. Ann Emerg Med 1995; 25:481.
  45. Lopez DM, Weingarten-Arams JS, Singer LP, Conway EE Jr. Relationship between arterial, mixed venous, and internal jugular carboxyhemoglobin concentrations at low, medium, and high concentrations in a piglet model of carbon monoxide toxicity. Crit Care Med 2000; 28:1998.
  46. Livshits Z, Lugassy DM, Shawn LK, Hoffman RS. Falsely low carboxyhemoglobin level after hydroxocobalamin therapy. N Engl J Med 2012; 367:1270.
  47. Lee J, Mukai D, Kreuter K, et al. Potential interference by hydroxocobalamin on cooximetry hemoglobin measurements during cyanide and smoke inhalation treatments. Ann Emerg Med 2007; 49:802.
  48. Borron SW, Uhl W, Nolting A, Hostalek U. Interference of the cyanide antidote hydroxocobalamin with carboxyhemoglobin measurements should not limit clinical use in suspected or confirmed cyanide poisoning. Ann Emerg Med 2007; 50:624.
  49. Baud F. Clarifications regarding interference of hydroxocobalamin with carboxyhemoglobin measurements in victims of smoke inhalation. Ann Emerg Med 2007; 50:625.
  50. Pace R, Bon Homme M, Hoffman RS, Lugassy D. Effects of hydroxocobalamin on carboxyhemoglobin measured under physiologic and pathologic conditions. Clin Toxicol (Phila) 2014; 52:647.
  51. Plante T, Harris D, Savitt J, et al. Carboxyhemoglobin monitored by bedside continuous CO-oximetry. J Trauma 2007; 63:1187.
  52. O'Malley GF. Non-invasive carbon monoxide measurement is not accurate. Ann Emerg Med 2006; 48:477.
  53. Touger M, Birnbaum A, Wang J, et al. Performance of the RAD-57 pulse CO-oximeter compared with standard laboratory carboxyhemoglobin measurement. Ann Emerg Med 2010; 56:382.
  54. Finelli PF, DiMario FJ Jr. Hemorrhagic infarction in white matter following acute carbon monoxide poisoning. Neurology 2004; 63:1102.
  55. Zagami AS, Lethlean AK, Mellick R. Delayed neurological deterioration following carbon monoxide poisoning: MRI findings. J Neurol 1993; 240:113.
  56. Teksam M, Casey SO, Michel E, et al. Diffusion-weighted MR imaging findings in carbon monoxide poisoning. Neuroradiology 2002; 44:109.
  57. Kim JH, Chang KH, Song IC, et al. Delayed encephalopathy of acute carbon monoxide intoxication: diffusivity of cerebral white matter lesions. AJNR Am J Neuroradiol 2003; 24:1592.
  58. Chu K, Jung KH, Kim HJ, et al. Diffusion-weighted MRI and 99mTc-HMPAO SPECT in delayed relapsing type of carbon monoxide poisoning: evidence of delayed cytotoxic edema. Eur Neurol 2004; 51:98.
  59. Hampson NB, Scott KL, Zmaeff JL. Carboxyhemoglobin measurement by hospitals: implications for the diagnosis of carbon monoxide poisoning. J Emerg Med 2006; 31:13.
  60. Hampson NB, Dunford RG, Kramer CC, Norkool DM. Selection criteria utilized for hyperbaric oxygen treatment of carbon monoxide poisoning. J Emerg Med 1995; 13:227.
  61. Leach RM, Rees PJ, Wilmshurst P. Hyperbaric oxygen therapy. BMJ 1998; 317:1140.
  62. Ziser A, Shupak A, Halpern P, et al. Delayed hyperbaric oxygen treatment for acute carbon monoxide poisoning. Br Med J (Clin Res Ed) 1984; 289:960.
  63. Goulon M, Barois, Rapin M, et al. Carbon monoxide poisoning and acute anoxia due to breathing coal gas and hydrocarbons. J Hyperbar MEd 1986; 1:23. http://archive.rubicon-foundation.org/xmlui/handle/123456789/4302 (Accessed on October 06, 2011).
  64. Weaver LK, Hopkins RO, Chan KJ, et al. Hyperbaric oxygen for acute carbon monoxide poisoning. N Engl J Med 2002; 347:1057.
  65. Ducassé JL, Celsis P, Marc-Vergnes JP. Non-comatose patients with acute carbon monoxide poisoning: hyperbaric or normobaric oxygenation? Undersea Hyperb Med 1995; 22:9.
  66. Scheinkestel CD, Bailey M, Myles PS, et al. Hyperbaric or normobaric oxygen for acute carbon monoxide poisoning: a randomised controlled clinical trial. Med J Aust 1999; 170:203.
  67. Raphael JC, Elkharrat D, Jars-Guincestre MC, et al. Trial of normobaric and hyperbaric oxygen for acute carbon monoxide intoxication. Lancet 1989; 2:414.
  68. Juurlink DN, Buckley NA, Stanbrook MB, et al. Hyperbaric oxygen for carbon monoxide poisoning. Cochrane Database Syst Rev 2005; :CD002041.
  69. Annane D, Chadda K, Gajdos P, et al. Hyperbaric oxygen therapy for acute domestic carbon monoxide poisoning: two randomized controlled trials. Intensive Care Med 2011; 37:486.
  70. Buckley NA, Juurlink DN, Isbister G, et al. Hyperbaric oxygen for carbon monoxide poisoning. Cochrane Database Syst Rev 2011; :CD002041.
  71. Koren G, Sharav T, Pastuszak A, et al. A multicenter, prospective study of fetal outcome following accidental carbon monoxide poisoning in pregnancy. Reprod Toxicol 1991; 5:397.
  72. Elkharrat D, Raphael JC, Korach JM, et al. Acute carbon monoxide intoxication and hyperbaric oxygen in pregnancy. Intensive Care Med 1991; 17:289.
  73. Van Hoesen KB, Camporesi EM, Moon RE, et al. Should hyperbaric oxygen be used to treat the pregnant patient for acute carbon monoxide poisoning? A case report and literature review. JAMA 1989; 261:1039.
  74. Towers CV, Corcoran VA. Influence of carbon monoxide poisoning on the fetal heart monitor tracing: a report of 3 cases. J Reprod Med 2009; 54:184.
  75. Fisher JA, Rucker J, Sommer LZ, et al. Isocapnic hyperpnea accelerates carbon monoxide elimination. Am J Respir Crit Care Med 1999; 159:1289.
  76. Takeuchi A, Vesely A, Rucker J, et al. A simple "new" method to accelerate clearance of carbon monoxide. Am J Respir Crit Care Med 2000; 161:1816.
  77. Rudge FW. Carbon monoxide poisoning in infants: treatment with hyperbaric oxygen. South Med J 1993; 86:334.
  78. Meert KL, Heidemann SM, Sarnaik AP. Outcome of children with carbon monoxide poisoning treated with normobaric oxygen. J Trauma 1998; 44:149.
  79. Kim JK, Coe CJ. Clinical study on carbon monoxide intoxication in children. Yonsei Med J 1987; 28:266.
  80. Cho CH, Chiu NC, Ho CS, Peng CC. Carbon monoxide poisoning in children. Pediatr Neonatol 2008; 49:121.
  81. Waisman D, Shupak A, Weisz G, Melamed Y. Hyperbaric oxygen therapy in the pediatric patient: the experience of the Israel Naval Medical Institute. Pediatrics 1998; 102:E53.
  82. Hampson NB, Courtney TG, Holm JR. Diffusion of carbon monoxide through gypsum wallboard. JAMA 2013; 310:745.