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Carbon Monoxide Poisoning Associated with a Propane-Powered Floor Burnisher -- Vermont, 1992

On July 28, 1992, two employees of a pharmacy in Vermont fainted within four hours after arriving for work; at a local hospital emergency department, carbon monoxide (CO) poisoning was diagnosed based on elevated carboxyhemoglobin (HbCO) levels. The pharmacy was evacuated, and the remaining eight employees were transported to the hospital for evaluation. Further investigation by the Vermont Department of Health (VDH) revealed that, on July 24, one of the employees had fainted, but CO poisoning was not suspected, and vasovagal syncope was diagnosed. This report summarizes the investigation of these cases by VDH.

A case of CO poisoning was defined as an arterial HbCO greater than or equal to 2% (for nonsmokers) or greater than or equal to 9% (for smokers) (1) in an employee who worked at the pharmacy on July 28. Based on analysis of arterial blood samples, nine of the 10 employees met the case definition; six were women. The mean age was 26.8 years (range: 17-42 years). Reported symptoms included headache (nine patients), lightheadedness (seven), tunnel vision (five), nausea/vomiting (four), syncope (two), difficulty breathing (two), chest pain (two), and decreased hearing (one). Serum samples were taken from six case-patients within 1-1/2 hours of exposure and from the other three case-patients within 3 hours of exposure. Mean HbCO was 16.6% (range: 6.7%-25.3%). Three patients received hyperbaric oxygen therapy: one had psychometric test abnormalities, and two had syncope without psychometric testing. All nine patients recovered.

On both July 24 and July 28, the store's floors had been cleaned with a liquid propane-powered floor burnisher by a subcontractor to a cleaning service company. The floor burnisher was independently owned and operated. On both days, the subcontractor had cleaned and polished the pharmacy floors before employees arrived. No cases of illness consistent with CO poisoning were reported among cleaning service employees.

The Division of Occupational and Radiological Health, VDH, impounded the burnisher and tested its emissions 2 days after the incident. Readings obtained outdoors from the burnisher's exhaust pipe reached 2000 parts per million (ppm) CO after less than 1 minute of measurement, 3000 ppm while idling, and 50,000 ppm at full throttle. All other possible sources of CO (i.e., heating and air-conditioning system, water-heater system, and truck traffic outside the store) were excluded as causes of the exposure.

HbCO levels among case-patients were used to estimate CO concentration in the work environment by the Coburn equation (2); this approach estimated that, on the morning of exposure, the CO concentration in the pharmacy was 507-1127 ppm. The Occupational Safety and Health Administration (OSHA) standard for CO is 50 ppm averaged over an 8-hour work shift and a ceiling level of 200 ppm, not to be exceeded at any time. The store's ventilation system used 100% recirculated air.

As a result of this investigation, the pharmacy and the cleaning contractor and subcontractor were fined. VDH recommended that liquid propane-powered burnishers be replaced with electric-powered burnishers and that CO alarms be installed if use of liquid propane-powered machines continued. Reported by: K Uraneck, MD, Southwestern Vermont Medical Center, Bennington; R McCandless, MPH, S Meyer, R Houseknecht, PhD, L Paulozzi, MD, State Epidemiologist, Vermont Dept of Health. Div of Field Epidemiology, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Unintentional exposure to CO is a major environmental hazard in the United States (3,4): each year, approximately 10,000 persons seek medical attention because of CO intoxication (5). Unintentional deaths attributable to CO poisoning result primarily from combustion of gasoline in motor vehicles, coal for heating or cooking, kerosene, and wood (3,6). In contrast to these fuels, propane -- the source of fuel involved in this report -- normally undergoes complete combustion in the presence of sufficient oxygen, producing nontoxic CO2 and water vapor (7); only when the oxygen supply at the point of combustion is inadequate does combustion of propane produce CO.

Symptoms of mild CO poisoning are nonspecific, and affected persons may not seek medical care. Because the cleaning service employees involved in the episode described in this report were exposed to elevated CO levels for limited periods (i.e., less than 1 hour), they may not have suffered ill effects of exposure. Pharmacy employees likely were exposed to peak CO levels on arrival to work and to elevated levels throughout the day.

The floor burnisher involved in this incident was factory-labeled with a warning to "shut off the engine if headache occurs and check emissions." OSHA permissible exposure levels regulate indoor air quality but do not require that such machines meet emission standards or receive routine maintenance. The most likely cause of CO poisoning in this case was failure to maintain or routinely service the burnisher. In addition, inadequate ventilation may have contributed to elevated concentrations of CO in the work environment. Episodes of CO poisoning, such as that described in this report, can be prevented by using only electric burnishers indoors, maintaining and routinely servicing fuel-burning burnishers, ensuring proper ventilation of the workplace, and educating persons regarding the signs and symptoms of CO poisoning.

Deaths resulting from CO poisoning are more common in winter months (3). Prevention efforts should be aimed at persons who live in homes with old heating systems, gas-powered space heaters, or wood stoves. Proper use and maintenance of such home-heating systems and cleaning of obstructed chimneys can prevent CO poisoning in the home.


  1. CDC. Unintentional deaths from carbon monoxide poisoning -- Michigan, 1987-1989. MMWR 1992;41:881-3,889.

  2. Coburn RF, Forster RE, Kane PB. Considerations of the physiology and variables that determine the blood carboxyhemoglobin concentration in man. J Clin Invest 1965;41:1899-910.

  3. Cobb N, Etzel RA. Unintentional carbon monoxide-related deaths in the United States, 1979-1988. JAMA 1991;266:659-63.

  4. CDC. Unintentional carbon monoxide poisoning following a winter storm -- Washington, January 1993. MMWR 1993;42:109-11.

  5. Schaplowsky AF, Oglesbay FB, Morrison JH, Gallagher RE, Berman W. Carbon monoxide contamination of the living environment: a national survey of home air and children's blood. Journal of Environmental Health 1974;36:569-73.

  6. Baron RC, Backer RC, Sopher IM. Fatal unintended carbon monoxide poisoning in West Virginia from nonvehicular sources. Am J Public Health 1989;79:1656-8.

  7. American Gas Association. Fundamentals of gas combustion. Arlington, Virginia: American Gas Association, 1973; catalog no. XH0373.

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