Skip directly to site content Skip directly to page options Skip directly to A-Z link


Centers for Disease Control and Prevention. CDC twenty four seven. Saving Lives, Protecting People
															Search
		×
			NIOSH
			NIOSH
				All CDC
				Submit
			For a full list of topics:A-Z Index
			Advanced Search
		Advanced Search


The National Institute for Occupational Safety and Health (NIOSH)


Facebook
        Twitter
        LinkedIn
        Syndicate





Two Maintenance Workers Die After Inhaling Hydrogen Sulfide in Manhole										Related Pages
										FACE 8928
INTRODUCTION
The National Institute for Occupational Safety and Health (NIOSH), Division of Safety Research (DSR), performs Fatal Accident Circumstances and Epidemiology (FACE) investigations when a participating state reports an occupational fatality and requests technical assistance. The goal of these evaluations is to prevent fatal work injuries in the future by studying the working environment, the worker, the task the worker was performing, the tools the worker was using, the energy exchange resulting in fatal injury, and the role of management in controlling how these factors interact.
On January 31, 1989, a 29-year-old male maintenance worker (the victim) entered a sewer manhole to repair a pipe, and collapsed at the bottom. In a rescue attempt, a 43-year-old male maintenance worker (co-worker victim) entered the manhole and also collapsed. Both workers (hereinafter referred to as initial victim and co-worker victim) were pronounced dead at the scene.

CONTACTS/ACTIVITIES
An industry association notified DSR of this multiple fatality and requested technical assistance. On April 5 and 6, 1989, a DSR research industrial hygienist met with the state OSHA compliance director and the company vice president to gather information, and traveled to the site of the incident to conduct an investigation.

OVERVIEW OF EMPLOYER’S SAFETY PROGRAM
The employer is an animal hide tanning company with 24 employees. The company operates a plant which has been in existence for 27 years (4 years under its present ownership). Most of the employees are tanning laborers (12 employees), drum operators (3 employees), and maintenance workers (2 employees). The victim had been with the company for nearly 4 years. Two months before the incident he had been promoted to the position of maintenance worker. The co-worker had been with the company for 6 years. He had been a maintenance worker for the last 4 years.
The company has a safety committee consisting of the two department heads, a union steward, and a foreman. The committee meets each week to discuss and follow up on needed safety improvements at the plant. Material safety data sheets (MSDS) on the various chemicals used in the plant are available throughout the plant. The company has a written safety policy consisting of plant safety rules and procedures for machine safety, chemical safety, and manhole entry. However, none of these rules and procedures were implemented. In addition, regular safety meetings for plant workers were not held.

SYNOPSIS OF EVENTS
The plant uses up to 120,000 gallons of water per day to process animal hides. After primary treatment, the wastewater is discharged into a series of lagoons approximately 400 yards from the plant. A gate valve located in a concrete manhole between a retention lagoon and a discharge lagoon regulates the flow of wastewater discharged. The manhole is 10 feet deep with an inside diameter of 4 feet. The top of the manhole has a 2-foot-square opening with a locked steel cover. Steel rungs on the inside of the manhole provide access to the bottom.
The manhole normally operates with about 3 feet of wastewater at the bottom. Rising vertically from a horizontal pipe at the bottom of the manhole is a 12-inch-diameter plastic overflow pipe. This pipe extends to 18 inches below ground level. The wastewater discharge volume was periodically adjusted by a worker who would partially enter the manhole (to about shoulder height and without entering the water), reach over and turn the gate valve. This adjustment was made on a routine basis without testing or ventilating the manhole atmosphere. (Since the incident, the company has extended the valve stem to a level above the ground, thereby eliminating the need for workers to routinely enter the manhole to adjust the valve.)
On the day of the incident the maintenance foreman assigned the two maintenance workers (initial victim and co-worker victim) the task of repairing a crack in the top of the overflow pipe. Although there were no eyewitnesses, evidence suggests that at about 11:00 a.m. the initial victim entered the manhole without first testing and ventilating the inside. Presumably, the initial victim, while standing on the steel rungs inside the manhole, began to repair the broken pipe with the co-worker victim observing the work from the top, handing down tools and supplies as needed. Hard hats and steel toe boots were the only personal protective equipment worn by the workers. While repairing the broken pipe, the initial victim was apparently overcome by hydrogen sulfide gas. He fell into approximately 3 feet of wastewater and sludge at the bottom of the manhole. Presumably in a rescue attempt, the co-worker victim entered the manhole, also lost consciousness, and fell to the bottom.
At about 11:45 a.m. , the maintenance foreman came to the manhole to tell the two workers it was lunchtime. When he looked into the manhole, he saw the co-worker victim at the bottom facedown in the water. The foreman did not see the initial victim, who was totally submerged in the wastewater. The foreman entered the manhole in an attempt to pull the co-worker victim out, but could not move him. The foreman became dizzy and felt like he was losing consciousness, so he climbed out. He then fell unconscious on the ground next to the manhole. When he regained consciousness approximately 15 minutes later, he ran to the plant office and notified plant personnel of the emergency. A call was placed to the emergency medical service (EMS) and the local fire department while four plant workers ran to the site. Another plant worker, who had been a local volunteer fire fighter, grabbed a self-contained breathing apparatus (SCBA) from the plant office and drove to the manhole site. The four plant workers who had arrived on foot each briefly entered the manhole in unsuccessful rescue attempts. None of these workers wore respiratory protection. They were all able to exit the manhole without any noticeable ill effects. The worker who arrived with the SCBA entered the manhole wearing the SCBA, but was also unsuccessful in his rescue attempt.
Fire fighters from the local fire department arrived at the scene approximately 15 minutes after being notified. one of the fire fighters donned an SCBA, entered the manhole and tied a rope around the co-worker victim’s chest. Rescue personnel then hoisted him up out of the manhole. The initial victim’s body was located and removed from the manhole in the same manner. When local EMS personnel arrived, they noted that the initial victim and co-worker victim were obviously dead for some time. Therefore, cardiopulmonary resuscitation was not attempted and the county coroner pronounced both workers dead at the scene. The foreman was hospitalized, treated for hydrogen sulfide exposure, and released 2 days later. The other five plant workers and the fire fighter who entered the manhole were treated for hydrogen sulfide exposure and released the same day.
Six days after the incident, a compliance officer from the state OSHA office conducted an investigation. During the investigation the atmosphere of the manhole was tested for hydrogen sulfide (H2S). At first, a gas monitoring device capable of measuring concentrations up to 100 parts per million (ppm) was used. When measurements indicated that the concentration of H2S at the bottom of the manhole exceeded 100 ppm, a gas monitoring device capable of measuring H2S concentrations up to 500 ppm was used. A measurement of 200 ppm H2S was obtained just inside the manhole opening.

CAUSE OF DEATH
The medical examiner listed the cause of death for both workers as anoxia due to hydrogen sulfide inhalation.

RECOMMENDATIONS/DISCUSSION
**Recommendation #1: All employers should develop and implement a safety program to protect their employees.**
Discussion: The company did not have a formal safety program established. Although the company had written safety rules and procedures, they were not implemented. There was also no safety training or safety meetings conducted for plant workers. A logical first step in developing a safety program is to identify all potential hazards. one way is by analyzing the sequential steps in routine operations to identify potential hazards, and attempting to develop procedures or other control measures which effectively eliminate or reduce the hazards. This type of analysis is known as job hazard analysis. Additionally, each specific job involves hazards particular to that job or the working environment. The company should therefore develop and implement a safety program as outlined in NIOSH publications 77-101, “Health and Safety Guide for the Tanning Industry,” and 76-157, “Good Work Practices For Tannery Workers.”

**Recommendation #2: The employer should develop and implement specific confined space entry procedures for each type of confined space.**
Discussion: Although the company had confined space procedures for entering the sewer manhole, they were not implemented. Also, the company’s existing confined space procedures do not fully address every basic procedure; however, if the existing procedures had been closely followed, the two fatalities in this incident may have been prevented. The company has other types of confined spaces (i.e., drums, pits, tanks, etc.) with no written entry procedures. Although these types of confined spaces are not entered on a routine or even an occasional basis, they should still be covered by specific procedures for entry. The company should therefore develop and implement a confined space entry program as outlined in NIOSH publications 80-106, “Working in Confined Spaces,” and 87-113, “A Guide to Safety in Confined Spaces.” At a minimum, the following items should be addressed for each type of confined space:
1. Is entry necessary? Can the assigned task be completed from the outside?
2. Has a confined space safe entry permit been issued by the company?
3. Are confined spaces posted with warning signs and are confined space procedures posted where they will be noticed by employees?
4. If entry is to be made, has the air quality in the confined space been tested for safety based on the following criteria:
149 oxygen supply at least 19.5%
149 Flammable range less than 10% of the lower explosive limit
Absence of toxic air contaminants5. Have employees and supervisors been trained in the selection and use of:
protective clothing,
respiratory protection,
hard hats,
eye protection,
gloves,
lifelines,
and emergency rescue equipment?
6. Have employees been trained for confined space entry?
7. Are confined space safe work practices discussed in safety meetings?
8. Have employees been trained in confined space rescue procedures?
9. Is ventilation equipment available and/or used?
10. Is the air quality tested when the ventilation system is operating?

**Recommendation #3: The employer should develop and implement a comprehensive respirator program as required by 29 CFR 1910.134, including either quantitative or qualitative fit testing and employee training in the use and limitations of SCBA and air-purifying respirators.**
Discussion: Although the company had an SCBA in the office and provides escape only hydrogen sulfide gas masks (not for confined space entry) for plant workers and drum operators, employees are not trained in their use and limitations. Employees are not given physical examinations to determine if they are capable of wearing a respirator. It should be noted that 3 months prior to this incident, a state OSHA compliance officer had cited the company for failure to provide an employee respirator program. The absence of a respirator program contributed to the fatalities and the potential hazards associated with the unsuccessful worker rescue efforts in this incident. Respirators should be selected according to criteria in the “NIOSH Respirator Decision Logic” (DHHS (NIOSH) Publication No. 87-108). Additional information on the characteristics and use of respirators is available in the “NIOSH Guide to Industrial Respiratory Protection” (DHHS (NIOSH) Publication No. 87-116).

Return to In-house FACE reports
							
					
						Page last reviewed:  November 18, 2015					Content source: 	National Institute for Occupational Safety and Health homeWorkplace Safety and Health Topics
Fatality Assessment and Control Evaluation(FACE) Programplus icon
New Content
About the Program
Investigations
NIOSH FACE Reports
State FACE Reports
Resourcesplus icon
Agriculture
Commercial Fishing
Construction
Energy Production
Landscaping
Logging
Robotics
Waste Management
Confined Space
Electrocution
Falls
Machine Related
Motor Vehicle
Trenching
Other
Crossing Guards
Hispanic
Youth
Contact Us To receive the NIOSH eNews newsletter, enter your email address: Email Address			What's this?				Submit
 Contact FACE Nancy Romano, M.S., CSHM
FACE Project Officer
Fatality Investigations Team
Division of Safety Research
NIOSHnioshface@cdc.gov **Press Inquiries**nioshmedia@cdc.gov
 Related Topics Traumatic Occupational Injuries
Fire Fighter Fatality Investigation and Prevention Program
Law Enforcement Officer Motor Vehicle Safety
 Follow NIOSH Facebook
Pinterest
Twitter
YouTube
 NIOSH Homepage NIOSH A-Z
Workplace Safety & Health Topics
Publications and Products
Programs
Contact NIOSH


About CDC
					Contact Us
					800-232-4636
 Facebook Twitter Instagram LinkedIn Youtube Pinterest Snapchat
 CONTACT CDC
				Contact Us
							Call 800-232-4636
							Email Us
			ABOUT CDC
				About CDC
							Jobs
							Funding
			POLICIES
				Accessibility
							External Links
							Privacy
							Policies
							No Fear Act
							FOIA
							OIG
							Nondiscrimination
							Vulnerability Disclosure Policy
			CONNECT WITH US
				Facebook
								Twitter
								Instagram
								LinkedIn
							Youtube
								Pinterest
								Snapchat
								Email
			LANGUAGES
				Español
							繁體中文
							Tiếng Việt
							한국어
							Tagalog
							Русский
							العربية
							Kreyòl Ayisyen
							Français
							Polski
							Português
							Italiano
							Deutsch
							日本語
							فارسی
							English


U.S. Department of Health & Human Services
			Accessibility
			External Links
			Privacy
			Policies
			No Fear Act
			FOIA
			Nondiscrimination
			OIG
			Vulnerability Disclosure Policy
			USA.gov


Exit Notification / Disclaimer Policy Close
 Links with this icon  indicate that you are leaving the CDC website. The Centers for Disease Control and Prevention (CDC) cannot attest to the accuracy of a non-federal website.
				Linking to a non-federal website does not constitute an endorsement by CDC or any of its employees of the sponsors or the information and products presented on the website.
				You will be subject to the destination website's privacy policy when you follow the link.
				CDC is not responsible for Section 508 compliance (accessibility) on other federal or private website. Website Disclaimers
 Cancel Continue