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American Journal of Forensic Medicine & Pathology:
Case Report

A Suicide Using a Homemade Carbon Monoxide “Death Machine”

Prahlow, Joseph A. MD*; Doyle, Barrett W.†

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From the *South Bend Medical Foundation and Indiana University School of Medicine–South Bend Center for Medical Education at the University of Notre Dame, South Bend, Indiana; and the †Porter County Coroner's Office, Valparaiso, Indiana.

Manuscript received October 15, 2004; accepted January 10, 2005.

Reprints: Joseph A. Prahlow, MD, South Bend Medical Foundation, 530 N. Lafayette Boulevard, South Bend, IN 46601. E-mail:

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Deaths related to carbon monoxide (CO) poisoning are common. Most represent accidents and suicides, and most result from CO production via the incomplete combustion of carbon-containing substances. Suicide via CO toxicity is not uncommon and typically involves the use of motor-vehicle exhaust as a source of CO. Presented herein is a case of suicidal CO poisoning in which the CO was produced via a chemical reaction between formic acid and sulfuric acid within a homemade device.

Deaths related to carbon monoxide (CO) inhalation are common. Such deaths are usually related to situations involving the incomplete combustion of carbon-containing (organic) materials.1–3 Examples include deaths due to smoke and soot inhalation occurring in fires, deaths occurring as a result of improper function or ventilation of cooking or heating equipment, and deaths due to exhaust produced by internal combustion engines.1–3 Although the incomplete combustion of organic material is responsible for a majority of the CO-related deaths investigated by medical examiners and coroners, it is not the only method of CO production. For example, CO can be formed in vivo via hepatic metabolism of methylene chloride (paint thinner/stripper).1,3 Other sources of CO include various industrial processes and chemical reactions.1,3 Presented herein is a case of suicidal CO inhalation in which the victim produced CO by combining formic acid and sulfuric acid in a homemade device.

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The victim was a 21-year-old unemployed male, living at home with his mother and his 2 younger siblings. He was considered a “loner” and frequently spent a majority of his time in his bedroom, watching television or accessing the Internet via his computer. There was no known drug-abuse history. He had been referred for psychiatric evaluation when he was 20 years old, was thought to be struggling with depression at that time, but had not followed through with recommended therapy. He was found dead in his bedroom closet by his mother when she went to check on him (Fig. 1). She found the bedroom door and closet door both taped shut from the inside with masking tape. She immediately called 911. Emergency responders, including police and medical personnel, determined that the victim was dead (Fig. 2). The first police officer to arrive at the scene noted a “chemical odor.” The coroner's office was notified, and police and coroner's office personnel conducted a scene investigation. Near the body, there was a homemade device made of 2 inverted 5-gallon buckets connected by clear plastic hosing and a shutoff valve on the inverted bottom of one of the buckets (Fig. 3). One of the buckets was leaking a substance that appeared to be melting the underlying carpet. Other items identified in the bedroom and/or closet were multiple plastic garbage bags; an opened box of 33-gallon garbage bags; a tube of plastic model cement; a caulk-gun holding 1 tube of opened and partially used caulk; a yellow utility knife; various other tools, including several drill bits; 2 unmarked, capped, white plastic bottles, each containing residual clear fluid (Fig. 4); and 3 paper funnels, 1 of which appeared to contain burnt residue.

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Body examination revealed the classic, bright red lividity characteristic of CO poisoning. The remainder of the postmortem examination was unremarkable. The postmortem carboxyhemoglobin level was 64%. A routine drug screen was negative. A lengthy suicide note was found in the bedroom (Fig. 5). Subsequent investigation revealed that the 2 chemical containers found at the scene contained sulfuric acid and formic acid, both obtained from the same Internet science-laboratory supply company. Consultation with a chemistry professor confirmed the fact that the simple combination of sulfuric acid and formic acid produces CO. The cause of death was ruled carbon monoxide poisoning. The manner of death was ruled suicide.

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Carbon monoxide is a colorless, odorless gas that binds hemoglobin with greater than 200 times the affinity of oxygen.1,3 There are many sources of the poisonous gas, including automobile exhaust, heating systems, fires, and tobacco smoke.1–3 A majority of the sources of CO are considered processes involving the incomplete combustion of carbon-containing (organic) substances; however, other means of CO production are known. These include in vivo metabolism of exogenous methylene chloride,1,3 endogenous production via catabolism of heme proteins,1 postmortem production via putrefaction of hemoglobin, myoglobin and other substances,4 and various chemical/industrial reactions.1 As forensic pathologists and death investigators are well aware, most CO deaths are related to CO production via incomplete combustion of organic material. The case presented herein represents a rare situation where a CO-related death resulted from a CO-producing chemical reaction.

Among chemists, a well-known standard procedure for producing carbon monoxide in the laboratory is via the combination of sulfuric acid and formic acid.5 Each of the acids is readily available from various chemical supply sources. Formic acid (also known as methanoic acid) is well known as an irritant in the stings of various insects of the order Hymenoptera.6 It is also the principal irritant in the leaves of the stinging nettle.6 In industry, formic acid is used as a preservative, an antibacterial agent in livestock feed, and in the tanning of leather.6 In the “stability and reactivity” section of certain versions of formic acid's Material Safety Data Sheet (MSDS), sulfuric acid is listed as an incompatible material and carbon monoxide is listed as a hazardous decomposition product.7 The International Chemical Safety Card (ICSC) for formic acid specifically warns of the danger of combining formic acid with strong acids, such as sulfuric acid, as CO production results.8

Sulfuric acid (also known as “oil of vitriol” and battery acid) is a strong acid that has many industrial uses, including lead-acid battery production, fertilizer manufacturing, ore processing, chemical synthesis, wastewater processing, and oil refining.9 It is also one of the many chemical components of what is commonly referred to as “acid rain.”9 Sulfuric acid is an extremely corrosive chemical such that any contact with the substance can result in severe injury.9 Perhaps for this reason, CO production via combination of sulfuric and formic acid is not even addressed in sulfuric acid's ICSC10 or certain versions of its MSDS.11,12

In the case presented, the homemade device was originally discovered in the closet with the decedent (Figs. 1 and 3 show the buckets, after they had been moved from the closet). Based on a proposed reconstruction of the event, it was surmised that each of the inverted 5-gallon buckets originally separately contained sulfuric acid and formic acid. The clear hose connecting the 2 buckets allowed for mixture of the acids. The shutoff valve (which was in the open position) on the bottom of one of the inverted buckets allowed the newly produced CO gas to escape either directly into the enclosed closet or into a garbage bag, which was subsequently used by the victim for CO inhalation.

Investigation of the suicide presented herein failed to reveal an obvious source of information regarding the homemade apparatus used to produce CO. A medical literature search revealed a similar suicide previously reported in the German literature.13 In that case, a 35-year-old committed suicide by enclosing himself in a large plastic bag, within which he had placed plastic bags containing sulfuric acid and formic acid.13 His carboxyhemoglobin levels from various sites ranged from 30.3% to 93.4%.13 While it is possible that the victim had access to this German medical journal article, no evidence was found that suggested this. It is more likely that the victim discovered the method of CO production by searching various Internet sites dedicated to suicide.

A large number of books and Internet sites are geared toward persons intent on committing suicide.14–22 In most of the Internet sites viewed, carbon monoxide was advocated as a reliable method of suicide.17–19,21,22 Various sources of CO are advocated, including automobile exhaust,17,20–22 burning a charcoal grill indoors,22 and the purchase of “pure” CO from industrial gas supply companies;18 however, only 1 site was found that specifically mentions mixing sulfuric acid and formic acid.17 Interestingly, the same site describes another chemical reaction that can be used to produce CO: a combination of calcium carbonate, zinc, and heat produces calcium oxide, zinc oxide, and CO.17 Whether or not any of these or any other suicide Internet sites were the source of information for the victim in the presented case is unknown.

Another potential source of information for the victim in the present case could have been via the media coverage of various suicide-advocate organizations, such as the Hemlock Society.23 In fact, at the time of the suicide, media attention had recently focused on a newly devised “suicide machine” or “death machine,” introduced at a Hemlock Society meeting in January of 2003 by an internationally known euthanasia advocate from Australia.24–31 The device, named “COGEN” or “CO Generator” for its ability to generate CO,24,29–31 results in CO gas production by combining formic and sulfuric acids.31 Inhalation of the newly produced CO reportedly occurs via a nasal tube.26 According to media sources, the machine is patented, and the inventor had planned to sell the device for less than $100 each.26 As the device was not yet available for purchase when the victim in the current case committed suicide but the media stories about the “death machine” were available on the Internet, it is conceivable that he built his own “homemade” machine, based on some of the information available from the news stories.

The present case serves to alert the forensic community to this unusual form of suicide. Until recently, the production of CO by combining sulfuric acid and formic acid was not considered common knowledge; however, the recently introduced “death machine” and the media coverage accompanying it will likely result in more suicides via this method. Finally, death investigators and others are advised to be aware of the potential environmental/scene chemical hazards which may accompany such cases.

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1. Jentzen JM, Mont EK, Revercomb C. Volatiles and inhalants (chemical asphyxia). In: Froede RC, ed. Handbook of Forensic Pathology. 2nd ed. Chicago, IL: College of American Pathologists; 2003:237–242.

2. Cobb N, Etzel RA. Unintentional carbon monoxide-related deaths in the United States, 1979 through 1988. JAMA. 1991;266:659–663.

3. Sadovnikoff N, Varon J, Sternbach GL. Carbon monoxide poisoning: an occult epidemic. Postgrad Med. 1992;92:86–96.

4. Kojima T, Nishiyama Y, Yashiki M, et al. Postmortem formation of carbon monoxide. Forensic Sci Int. 1982;19:243–248.

5. Production of carbon monoxide. Available at: http// Accessed October 10, 2003.

6. Formic acid. In: Wikipedia: The Free Encyclopedia. Available at: Accessed March 11, 2004.

7. Material Safety Data Sheet: formic acid. Available at: Accessed March 11, 2004.

8. International Chemical Safety Cards: formic acid (ICSC: 0485). Available at: Accessed March 11, 2004.

9. Sulfuric acid. In: Wikipedia: The Free Encyclopedia. Available at: Accessed July 22, 2004.

10. International Chemical Safety Cards: sulfuric acid (ICSC: 0362). Available at: Accessed July 22, 2004.

11. Material Safety Data Sheet: sulfuric acid. Available at: Accessed March 11, 2004.

12. Material Safety Data Sheet: sulfuric acid. Available from General Chemical Corporation, 90 East Halsey Road, Pardippany, NJ 07054.

13. Wehr K, Schafer A. A case of unusual suicidal carbon monoxide intoxication. Archiv Kriminol. 1987;180:155–160.

14. Humphry D. Final Exit: The Practicalities of Self-Deliverance and Assisted Suicide for the Dying. 3rd ed. Addlestone, England: Delta; 2002.

15. Kevorkian J. Prescription Medicide: The Goodness of Planned Death. Amherst, NY: Prometheus Books; 1991.

16. Humphry D. Dying with Dignity. New York, NY: Random House Value Publishing; 1995.

17. A practical guide to suicide. Available at: Accessed June 29, 2004.

18. Hunt J. How to kill yourself using the inhalation of carbon monoxide gas. Available at: Accessed March 11, 2004.

19. The suicide machine: assisted suicide methods. Available at: Accessed March 11, 2004.

21. How to commit suicide. Available at: Accessed March 12, 2004.

22. Carbon monoxide (CO) poisoning as a method of suicide. Available at: Accessed March 11, 2004.

23. Accessed March 12, 2004.

24. Nitschke launches suicide machine. Sydney Morning Herald. December 3, 2002. Available at: Accessed March 12, 2004.

25. Goodenough P. Euthanasia campaigner unveils new suicide device. December 3, 2002. Available at: Accessed March 12, 2004.

26. Nitschke to unveil death machine. Age. January 6, 2003. Available at: Accessed March 12, 2004.

27. Bradley M. Nitschke's death machine seized. Age. January 11, 2003. Available at: Accessed March 12, 2004.

28. Australia MD to make new suicide machine. Associated Press. January 12, 2003. Available at: Accessed March 12, 2004.

29. Morgante M. Death machine to live again. Associated Press. January 13, 2003. Available at: Accessed March 12, 2004.

30. “Dr Death” demonstrates DIY suicide. Thomas Crosbie Media. May 31, 2003. Available at: Accessed March 12, 2004.

31. Nitschke reveals killing machine. Age. May 31, 2003. Available at: Accessed March 12, 2004.

Cited By:

This article has been cited 3 time(s).

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forensic science; suicide; carbon monoxide; formic acid; sulfuric acid; death machine

© 2005 Lippincott Williams & Wilkins, Inc.


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