1. Nitrogen: The Silent Killer
Stephen J. Wallace, PE, CSP
Senior Advisor - Safety, Infrastructure & Operations (NA-50)
November 9, 2017

2. Agenda
Introduction
Health effects
Statistics
Causes
Case studies
Good practices
Summary

3. Introduction
Experience with asphyxiation incidents
Investigated asphyxiation incidents
Presentation borrows heavily from a study I lead at the Chemical Safety Board
Although focused on nitrogen, anything that displaces oxygen is a potential hazard (e.g., carbon dioxide)

4. Introduction
The Silent Killer
Nitrogen makes up ~ 78% of air we breath; and some assume that it is not hazardous
• However, nitrogen is safe to breath only if mixed with an appropriate amount of oxygen
• Nitrogen asphyxiation has been approved as an execution method by some states
• High concentration of nitrogen (lower oxygen) cannot be detected by smell

5. Introduction
Nitrogen is used commercially as an inerting agent to prevent contaminants (including oxygen)
Nitrogen is ubiquitous in DOE facilities (e.g., gloveboxes, gas in dry pipe systems)
• Lower oxygen concentration has a range of effects on the body, including death

6. Health Effects O2 Conc (%) Possible Results 20.9 Normal
Some unnoticeable adverse physiological effects
Increased pulse and breathing rate, impaired thinking and attention, reduced coordination
Abnormal fatigue upon exertion, emotional upset, faulty coordination, poor judgment
Very poor judgment and coordination, impaired respiration that may cause permanent heart damage, nausea, and vomiting
<10 Inability to move, loss of consciousness, convulsions, death
Source: Compressed Gas Association

7. Statistics on Incidents
CSB reviewed nitrogen asphyxiation cases in the US between 1992 and 2002: • Majority in manufacturing and industrial settings, but several in other settings including laboratories • 85 incidents of nitrogen asphyxiation resulted in 80 deaths and 50 injuries • Contractors account for over 60% of the fatalities Context: These numbers only capture incidents that were reported and found during search, the true numbers are likely far higher. Though somewhat dated, this information shows that nitrogen asphyxiation is a significant concern.

8. Causes of Incidents
Majority of incidents occurred in and around confined spaces, though several occurred in “open” areas (e.g., inside buildings, outdoors near equipment)

9. Causes of Incidents
Causes of fatal incidents included: • Failure to detect an oxygen-deficient atmosphere in and around confined spaces • Mistakenly using nitrogen instead of breathing air • Improper rescue

10. Case Study: Near Confined Space
Three workers were cleaning filters in a hydrogen purifying tank • Tank was purged with nitrogen during cleaning • One worker leaned over a manway opening in the upper portion of the tank • He was found unconscious and later died

11. Case Study: Lack of Monitoring
A tank car at a refinery contained white mineral oil and an employee entered to clean it • The mineral oil was offloaded by injecting nitrogen gas into the car • The nitrogen was still present when the employee started to clean the car and he was asphyxiated

12. Case Study: Corrupt Breathing Air
Two contractors were cleaning tubes inside a boiler
• They wore supplied-air respirators connected to compressed air cylinders
• After the workers failed to respond to an air horn, they were found unconscious
• Follow-up testing of the air supply – manufactured by mixing oxygen and nitrogen – found that it contained less than 5% oxygen

13. Case Study: Mix up N2 and Air
A contract employee was chipping residue from a furnace
• He wore an airline respirator
• Two compressed gas lines were available; one was labeled “natural gas” and one was labeled “air”
• Once the respirator was in place, the employee was asphyxiated; the “air” line actually contained pure nitrogen

14. Case Study: Mix up; Rescue
The atmosphere inside a coated tank was tested and ventilated the day before work was to be performed inside
• A contractor entered the tank to clean it the next day and collapsed
• Two plant employees attempted rescue and were overcome; All three workers died
• The tank had mistakenly been ventilated with nitrogen instead of compressed air

15. Case Study: Mix up N2 and O2
A supplier mistakenly delivered a cylinder of nitrogen during a delivery of oxygen cylinders
• The nursing home employee mistakenly accepted the nitrogen tank
• The cylinder was labeled with a nitrogen label partially covering an oxygen label

16. Case Study: Mix up N2 and O2
• The tank had nitrogen-compatible fittings • A maintenance employee removed the fittings from an empty oxygen cylinder and used it as an adapter to connect the nitrogen tank to the oxygen system • Four patients died and six were injured

17. Case Study: Improper entry/rescue

18. Case Study: Improper entry/rescue
Contract workers noticed a roll of tape in a vessel they knew was inerted • Apparently, one worker entered the vessel to retrieve the tape • When the first worker went down, a second worker entered the vessel to save him • When the second worker went down, a third worker started to enter the vessel but stopped on the ladder before entering

19. Good Practices
Implement warning systems and continuous atmospheric monitoring of enclosures • Continuously monitor for oxygen-deficient, toxic, or explosive atmospheres • Employ warning systems including flashing lights, alarms, and auto-locking entryways; signs are not enough! • Use personnel monitors to indicate low oxygen concentrations • Remember the atmosphere can change

20. Good Practices
Ensure ventilation with fresh-air in confined and enclosed areas • Maintain continuous forced draft ventilation with fresh air before job begins and through completion • Ensure that ventilation systems are properly designed, evaluated, and maintained • Use warning systems to alert personnel if the system fails

21. Good Practices
Implement a system for the safe retrieval and rescue of workers • Employees in confined spaces should wear equipment to facilitate retrieval (e.g., body harness, anklets, lifeline) • Standby personnel present at all times and in constant communication with personnel inside • Personnel should not attempt rescue unless they are properly trained and equipped

22. Good Practices
Ensure the uninterrupted flow and integrity of breathing air • Ensure supplied air is not interrupted (e.g., secure alternate power sources for compressors, inspect hoses, restrict traffic) • Carry escape packs • Ensure the composition of supplied breathing air is correct • Continuously monitor the air supply

23. Good Practices
Prevent inadvertent mix-up of nitrogen and breathing air • Ensure personnel understand the reason for specific unique fittings. Do not fabricate “adapters” to defeat their purpose. • Ensure that cylinders are clearly labeled • Use color coding to identify systems

24. Good Practices
Develop and implement training programs for employees and contract personnel, including: • Proper use of ventilation, retrieval, air monitoring, and air supply systems • Safe practices for working in and around confined spaces, including rescue • Preventing mix-ups between breathing air and nitrogen • Implementing good hazard communication

25. • Asphyxiation hazards are present in DOE facilities
Summary
• Asphyxiation hazards are present in DOE facilities
• Low concentrations of oxygen quickly results in health hazards including death
• Safe practices and engineering controls including continuous monitoring, alarms, and interlocks must be used. Signs are not enough!
Note: One of the most fatal accidents in DOE history was an asphyxiation accident.

26. Any questions?