Fatal Occupational Injuries Involving Confined Spaces, 1997-2001

Farms in the Midwest and industrial places in the South accounted for 108 fatalities each during the five-year period.

Hazards in confined spaces are unpredictable or invisible, which makes them difficult to detect and avoid. According to the National Institute for Occupational Safety and Health, confined space hazards can be separated into two groups: physical hazards and atmospheric hazards. Physical hazards include engulfment, entry and exit complications, communication difficulties, thermal effects, falling objects, dangerous surfaces, electricity, and mechanical equipment. Atmospheric hazards include toxic gases and solvents, oxygen deficiency or displacement, and flammable gases.1,2

The Occupational Safety & Health Administration adds that the material being stored or used in such a space, the internal activities, or the effects of the external environment, also determine the hazards within confined spaces.3

While many studies cover atmospheric hazards in confined spaces, this article examines fatal occupational injuries from both physical and atmospheric hazards. Data from the Bureau of Labor Statistics (BLS) Census of Fatal Occupational Injuries (CFOI) program for the five-year period 1997 to 2001 were used for this study.4 CFOI provides an annual count of decedents fatally injured while working for all 50 states and the District of Columbia beginning in 1992.

Figure 1
Number of fatal occupational injuries in confined spaces, US, 1997-2001








Fatal injuries







A total of 458 fatal occupational injuries meeting the research definition were recorded in the period 1997-2001. Fatal injuries in confined spaces fluctuated from a low of 81 in 1998 to a high of 100 in 2000 during the five-year period, averaging 92 fatalities per year (see Figure 1).

When combined, nearly 40 percent of all confined space fatal occupational injuries occurred in the 4-hour period from 10 a.m. to 2 p.m.

Every four days during the study period, a worker died in a confined space. The confined spaces fatality rate was 0.07 fatal work injuries per 100,000 workers. However, in certain groups of workers a much higher risk of fatal occupational injury in confined spaces was found. For example, the relative risk of a confined space fatality in farming, forestry, and fishing occupations was more than nine times that for all industries. The risk to men was 64 times the risk of women. Also, self-employed workers were more than three times more likely to incur a fatal injury within a confined space than those who were not self-employed. Additionally, even while excluding mine cave-ins and roof falls from the confined space data, the mining industry registered the highest risk of fatal injury due to a confined space with a relative risk 10 times that of all industries.

Between 1997 and 2001, 246 fatal injuries occurred while workers were constructing, repairing, and cleaning, contributing 54 percent of confined space fatalities (see Figure 2). Of these, 101 fatal injuries resulted from repair and maintenance activities, while 57 occurred during cleaning and washing activities. While performing material handling operations, including loading and unloading materials, retrieving objects, and working with chemicals (except cleaning), a total of 78 workers were fatally injured. Another 48 workers were using or operating tools and machinery within confined spaces when fatally injured.

Figure 2
Number and percent distribution of fatal occupational injuries in confined spaces by worker activity, US, 1997-2001.

Worker activity

Fatal injuries





Constructing, repairing, cleaning



Repair, maintenance



Cleaning, washing



Construction, assembling, dismantling



Materials handling operations



Loading, unloading materials



Materials handling, n.e.c.*



Using or operating tools, machinery



Physical activity, n.e.c.



Protective service activities






Vehicular and transportation operations



All other activities



* n.e.c. means "not elsewhere classified." For example, the category "Materials handling, n.e.c." is a subcategory of "Materials Handling Operations" that includes anything fitting within materials handling operations that is not elsewhere classified.

The most frequent situation associated with fatal injuries in confined spaces involved a worker caught in or crushed in collapsing materials while working inside a silo or grain bin. Another frequent situation involved workers who were exposed to chemicals, including ammonia compounds, sulfur compounds, and certain oxides, while working in a factory or plant.

Figure 3
Features of fatal occupational injuries involving in confined spaces, 1997-2001.



Number of fatal injuries

Most frequent events

Caught in or crushed in collapsing materials


Exposure to caustic, noxious, or allergenic substances


Most frequent locations

Silo, grain bin


Factory, plant


Most frequent sources of injury

Food products-fresh or processed


Other chemicals


A total of 25 fatal injuries occurred to workers involved in rescue efforts, most of which were employed in an occupation other than professional rescue.5 Of these, rescuers died while saving the life of another 13 times in the five-year period. Private industry represented the largest group of these fatalities due to rescue activities, 80 percent having taken place on either industrial property or farm grounds. Nearly all 25 workers suffocated, drowned, or were poisoned during rescue efforts. Oxygen deficiency led as the event that took the most lives of rescuers.

A total of 97 confined space fatalities (22 percent) occurred between the hours of 10 a.m. and noon, and another 72 occurred between noon and 2 p.m. When combined, nearly 40 percent of all confined space fatal occupational injuries occurred in the 4-hour period from 10 a.m. to 2 p.m.

Figure 4: Time of fatal injury by percent distribution, U.S., 1997-2001.

Ninety-four percent (431 fatalities) of fatal injuries from confined space incidents involved private industry workers. The largest number of confined space cases was in agriculture, forestry, and fishing, which accounted for nearly one-fourth of all confined space fatalities. Manufacturing had 20 percent and construction had 19 percent.

Over 75 percent of all fatal occupational injuries involving confined spaces occurred in the Midwestern or Southern regions of the United States. Farms in the Midwest and industrial places in the South were the two locations with the highest number of fatal occupational injuries in confined spaces, accounting for 108 fatalities each from 1997 through 2001.

Figure 5
Relative risk of fatal injury due to confined spaces by occupation and industry, 1997-2001.


Total (all fatal injuries)

Relative risk*





Managerial and professional specialty



Technical, sales, and admin support



Service occupations



Farming, forestry, and fishing



Precision production, craft, and repair



Operators, fabricators, and laborers




Private industry



Agriculture, forestry, and fishing












Transportation and public utilities



Wholesale trade



Retail trade









* The relative risks were calculated using the formula (nr/totalr) where nr = fatality rate for the variable in question and totalr = 0.07, the fatality rate of the total confined space fatal injuries per 100,000 employed during the period 1997 to 2001. Fatality rates were calculated using the formula ((f/e)*100,000) where f = fatal occupational injuries for the variable in question and e = estimate of employment using Current Population Survey (CPS) data.

Operators, fabricators, and laborers were the victims in 175 fatal confined space incidents (or 38 percent of the five-year total), which was more than all other major occupation groups. Of these fatal injuries, 79 were incurred by laborers, including laborers in the construction industry. A total of 109 workers in farming occupations other than horticulture, nursery, and marine-life farms died due to fatal injuries in confined spaces.6 Approximately 65 percent of these 109 workers died in silos or grain bins. The top three events or exposures to farmers included:

  • Caught in or crushed in collapsing materials, resulting in 63 fatal injuries
  • Oxygen deficiency, resulting in 16 fatal injuries
  • Inhalation of substances, resulting in 15 fatal injuries

With a relative risk above 9.0 and a comparatively high frequency of fatal injury in confined spaces (109 out of 458 total), farming occupations merit particular concern. Approximately consistent with overall farming statistics, all of the reported decedents from confined space workplace fatalities were male. Interestingly, 97 percent of decedents were white, and 71 percent were self-employed. Seventy-four percent of these cases took place in the Midwest.

Agriculture, forestry, and fishing accounted for nearly one-fourth of all confined space fatalities. Manufacturing had 20 percent and construction had 19 percent.

Workers aged 65 or older made up the largest age group in farming to die within a confined space at 25 percent, 10 percent less than their share of all events in farming occupations. Workers aged 35 to 44 years old made up the second largest group of confined space fatalities with 21 percent. Silos and grain bins are the most hazardous of any location on farm premises, accounting for 71 deaths. Animal feed, cash grain crops, and field crops were the direct cause of death in 59 percent of cases. Sixty-three fatalities occurred when workers were caught in collapsing materials and were asphyxiated. Another 16 workers died due to oxygen deficiency, and 15 workers inhaled some type of toxic substance.

The data suggest that confined spaces have great potential for danger. Often the hazardous nature of the space in question goes undetected, resulting in sudden hazardous exposures with little warning. However, adhering to safety protocols can reduce the number of confined space fatal injuries each year. Twenty-two percent of all fatalities occurred between 10 a.m. and 12 p.m., indicating those working in confined spaces in the late morning hours should be especially cautious (see Figure 4).

Moreover, those working in agriculture occupations frequently put in more than 14-hour days, which could contribute to the high representation of farming, forestry, and fishing workers in confined space fatalities. Also, the data suggest there is not sufficient awareness of the dangers involved in working in commonplace silos and grain bins.

Additionally, untrained rescuers should be aware of protocol specific to confined space hazards. If workers can identify the dangers in their working environments and be aware of sources of injury, such as poisonous atmospheres, temperature extremes, and instability in grain bins, confined space fatalities can be avoided.

1. Bender, Thomas R., Ted A. Pettit, et al. Worker Deaths in Confined Spaces: A Summary of Surveillance Findings and Investigative Case Reports. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, DHHS (NIOSH) Publication Number 94-103, pp. 6-10.
2. More policy issue details can be found at OSHA's confined spaces Web site Safety and Health Topics: Confined Spaces, www.osha.gov/SLTC/confinedspaces.index.html.
3. Confined Space Hazards. Small Business Outreach Training Program Instructional Guide, May 1997, Des Plaines, IL. www.osha.gov/SLTC/smallbusiness/sec12.html.
4. For details regarding the methods of research employed, contact the author at the following: 202-691-6273, meyer_s@bls.gov, 2 Massachusetts Ave. NE, PSB--Room 3175, Washington, DC 20212.
5. Two methods were employed to determine the number of fatal injuries occurring within rescue efforts. First, BLS developed coding for the activity in which the worker was involved at the time of injury. In this case, code 440 is defined as rescuing or evacuating and resulted in 15 fatal injuries. Second, the narratives may be examined to identify rescuing activities, which resulted in 25 fatal injuries. However, both of these may be insufficient because these incidents are often unwitnessed. Also, it could be incorrectly assumed that multiple fatality incidents within confined spaces imply one of the decedents was rescuing the other(s).
6. Farming occupations consist of Standard Occupational Classification (SOC) system codes (developed by the Bureau of the Census) for farmers and farm managers, excluding horticultural farms, farm workers, and farm worker supervisors.

This article originally appeared in the November 2003 issue of Occupational Health & Safety.

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