National Center for Statistics & Analysis - Research & Development - 400 Seventh St. SW - Washington, DC 20590

U.S. Department 

of Transportation

National Highway 

Traffic Safety 

Administration 

April 2000 

 Fatalities Associated With Carbon Monoxide Poisoning 

 From Motor Vehicles, 1995-1997 

Introduction

NHTSA’s National Center for Statistics and 

Analysis (NCSA) recently completed a second 

study of data from the National Center for 

Health Statistics (NCHS) to obtain an estimate 

of the number of persons killed as a result of 

carbon monoxide (CO) poisoning by exhaust 

gases of motor vehicles. This note updates 

the results of the study done in 1996 to assess 

the extent of fatalities associated with CO 

poisoning from motor vehicles using the 

NCHS data for the 1993 calendar year 

(NHTSA, 1996). This study focuses on the 

extent to which moving, as opposed to 

stationary, motor vehicles are involved in CO 

poisoning deaths. In addition, the study 

examined the proportion of accidental, i.e., 

unintentional CO deaths; the vehicle location 

for accidental CO fatalities involving 

stationary vehicles, and the season of the year 

in which the greatest proportion of accidental 

CO deaths occur. 

Data for calendar years 1995-1997 were used 

in this study. NCHS obtains information on 

the cause(s) of death, as recorded on death 

certificates, from each of the fifty states, the 

District of Columbia, and the five boroughs of 

New York City. For the years 1995-97, the 

total number of fatalities due to CO poisoning 

decreased from 2,037 in 1995 to 1,678 in 

1997. The total number of fatalities recorded 

in 1993 as a result of CO poisoning was 

2,086. The majority of these fatalities 

involved stationary motor vehicles, ranging 

from 96 percent in 1995 to 97 percent in 1996 

and 96 percent in 1997 (95 percent in 1993). 

On an average, almost 84% of the CO 

fatalities involving stationary motor vehicles 

were classified as intentional, or suicide. For 

moving motor vehicles, this pattern was 

reversed, i.e., all of the CO fatalities involving 

moving vehicles were classified as 

unintentional or accidental. 

Methodology

The summary statistics of CO poisoning 

deaths due to motor vehicle exhaust gas have 

been generated by aggregating the 

International Classification of Diseases, 9th

Revision (ICD-9)1 Underlying Cause of Death 

Codes from the NCHS mortality data. Based 

on these underlying causes, the NCSA has 

adopted a listing comprised of fatalities due to 

CO poisoning from motor vehicle exhaust gas. 

 1

9th Revision, International 

Classification of Diseases, Department of Health 

and Human Services, 1989.

 The ICD-9 codes comprise a four-digit 

rubric. The fatalities along the various 

categories presented in this paper have been 

determined from the listing in the ICD-9 

classification manual [Refer HHS, 1989]. In 

some cases, the Record Axis (RA) codes in 

the NCHS file were used in tandem with the 

ICD-9 codes. The RA codes facilitate a more 

detailed description of the ICD-9 code. This 

detailed description is captured in the form of 

twenty RA codes. The RA codes are 

classified in a manner comparable to the 

underlying cause of death classification, 

Research Note
National Center for Statistics & Analysis - Research & Development - 400 Seventh St. SW - Washington, DC 20590

thereby facilitating joint analysis of the 20 RA 

codes, if available, and the underlying cause 

of death, which is death due to CO poisoning. 

 The underlying cause as well as the RA codes 

literally represent the 

information conveyed in the ICD-9 four-digit 

rubrics. Table 1 presents the combination of 

the Underlying Cause of Death and the RA 

codes used in this analysis. 

Table 1 : Underlying Cause of Death and RA Codes used to determine CO Deaths 

Nature of Death Underlying Cause of Death Record Axis Codes

Suicide 952.0 - 

Accidental 868.2 - Stationary Vehicles 

Unknown 982.0 - 

Suicide 952.0 809.0 to 825.9

Moving Vehicles Accidental 809.0 to 825.9 986

Table 2 presents the literal description of the ICD-9 codes used in this study.

Table 2 : Interpretation (ICD-9) of the Underlying Cause of Death and the RA codes 

ICD-9 Code ICD-9 Description

809.0 to 825.9 Motor Vehicle Traffic Accidents

868.2 Accidental Poisoning from Motor Vehicle Exhaust Gas (Not in Transit)

952.0 Suicide from Motor Vehicle Exhaust Gas (Stationary)

982.0 CO Poisoning, undetermined whether accidentally or purposely inflicted

986 Toxic Effect of CO

Table 3 presents total CO fatalities from 1995-1997, by stationary vs. moving motor vehicles. 

Table3 : Fatalities Associated with CO Poisoning in 1995-1997 

Nature of Death 1995 1996 1997 Total 

Suicide 

(%) 

1,663 

(84.7) 

1,511 

(84.2) 

1,368 

(84.6) 

4,542 

(84.5) 

Accidental 

(%) 

234 

(11.9) 

223 

(12.4) 

208 

(12.9) 

665 

(12.4) 

Stationary 

Vehicles 

Unknown 

(%) 

67 

(3.4) 

61 

(3.4) 

41 

(2.5) 

169 

(3.1) 

Moving Vehicles Suicide 0 0 0 0 

Accidental 73 59 61 193 
National Center for Statistics & Analysis - Research & Development - 400 Seventh St. SW - Washington, DC 20590

Total 2,037 1,854 1,678 5,569

The NCHS data indicated that 234 CO 

fatalities involving stationary motor vehicles 

were considered to be accidental in 1995, 

followed by 223 in 1996 and 208 in 1997. A 

CO fatality involving a stationary vehicle was 

one in which the death occurred either within 

or outside of the vehicle in an enclosed area. 

The majority of these fatalities, an average of 

60 percent, occurred with vehicles located at 

home, as opposed to on a public roadway or in 

other locations. Table 4 presents the 

distribution of accidental CO fatalities 

involving stationary vehicles by location. As 

indicated in Table 3, the total number of 

accidental CO fatalities involving stationary 

vehicles has decreased from 1995 to 1997 

(234 to 208). Thus, the number of accidental 

CO fatalities involving stationary motor 

vehicles has decreased from a high of 245 in 

1993. However, accidental CO deaths as a 

proportion of the total CO deaths in stationary 

vehicles, has increased from about 12 percent 

in 1995 to 13 percent in 1997.

Table 4 : Accidental CO Fatalities with Stationary Vehicles by Vehicle Location, 1995-1997 

Vehicle Location 1995 1996 1997 Total 

At Home 126

(53.8) 

149

(66.8) 

122

(58.6) 

397

(59.7) 

On Public Roadway 6

(2.6) 

7

(3.2) 

7

(3.4) 

20

(3.0) 

Other Locations 102

(43.6) 

67

(30.0) 

79

(38.0) 

248

(37.3) 

Total 234 223 208 665

For stationary and moving motor vehicles 

combined, a total of 307 accidental CO 

fatalities occurred in 1995 followed by 282 in 

1996 and 269 in 1997. Of these fatalities, the 

largest proportion, on an average, about 35 

percent occurred during the winter months of 

December, January, and February. Table 5 

presents the distribution of accidental CO 

fatalities from 1995 to 1997 by season of 

occurrence. 

Table 5: All Accidental CO Fatalities in 1995-1997 by Season of Occurrence

Season 1995 1996 1997 Total 

Fall 77

(25.1) 

62

(22.0) 

77

(28.6) 

216

(25.2) 

Winter 105

(34.2) 

109

(38.6) 

89

(33.1) 

303

(35.3) 

Spring 76

(24.7) 

63

(22.3) 

71

(26.4) 

210

(24.5) 
National Center for Statistics & Analysis - Research & Development - 400 Seventh St. SW - Washington, DC 20590

Season 1995 1996 1997 Total 

Summer 49

(16.0) 

48

(17.1) 

32

(11.9) 

129

(15.0) 

Total 307 282 269 858

In the summer months, namely June, July and 

August, the incidence of accidental deaths due 

to CO poisoning was least compared to the 

other seasons, with an average of about 15 

percent of the accidental CO deaths for the 

whole year. 

References

National Highway Traffic Safety 

Administration (1996). Fatalities associated 

with Carbon Monoxide Poisoning From 

Motor Vehicles in 1993. Washington, D.C.: 

Department of Transportation. 

Department of Health and Human Services 

(1989), International Classification of 

Diseases, 9th Revision (ICD-9). 

For additional copies of this research note, 

please call (202) 366-5388 or fax your request 

to (202) 366-7078. For questions, please 

contact Rajesh Subramanian of the National 

Center of Statistics and Analysis, at (202) 

366-5371. This research note and other 

general information on highway traffic safety 

may be accessed by Internet users at 

http://www.nhtsa.dot.gov/people/ncsa.