Dangers of Nitrogen

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by Rudi Nieuwoudt

Nitrogen, as an inert gas, is said to be a component of the air we breathe but can pose a serious threat because it is an odourless, tasteless gas that completely displaces oxygen. Nitrogen has a low heat-transfer capability and does not flow very fast. The result is that it tends to stay in a place in a cloud. If you are caught in nitrogen cloud, death can occur with little warning.

Nitrogen gas is not a “poison” in the traditional sense but it presents a hazard of asphyxiation when it displaces oxygen. Breathing an oxygen deficient atmosphere can have serious and immediate effects, including unconsciousness after only 1 or 2 breaths.

The air that we breathe is 78% nitrogen and 21% oxygen. According to studies, the maximum “safe level” of oxygen is said to be 23.5%. 21% is normal and 19.5% is considered to be the minimum “safe level.” At 15-19% the first sign of hypoxia or insufficient oxygen in the body occurs, resulting in a decreased ability to work strenuously and may induce symptoms in people with heart, lung, or circulatory problems.

What are the uses of Nitrogen

Strangely enough this gas that can kill is mostly used in safety applications:

As a Gas:

  • for inerting equipment to prevent flammable atmospheres
  • for preparing equipment for maintenance by purging out hydrocarbons
  • for removal of air / oxygen in equipment before start up
  • for blanketing tanks to prevent the ingress of air
  • for specific welding operations
  • for "mothballing" equipment to avoid the rusting process
  • for use as fire-fighting agent as it removes air

 As a Liquid:

  • for cooling purposes in the laboratory, freezing a pipeline, etc
  • for storage and transportation of Nitrogen in large quantities

How can you protect yourself?

Permit to Work System

If the confined space contains an actual or potential atmospheric hazard, it's a permit-required confined space.

Continuous Atmospheric Monitoring

Because the atmosphere in a confined space may be unfit for breathing prior to entry, or it may change over time, the atmosphere in the entire confined space should be tested and confirmed safe before workers enter the space and should be monitored continuously while workers are in the space.

Ensure Ventilation with Fresh Air

Any time workers are entering a confined space or a small or enclosed area without wearing a supplied-air breathing apparatus, it is critical to provide continuous ventilation with forced-draft fresh air. While fresh-air ventilation is not an option when workers are entering a pure nitrogen environment such as when workers are changing a catalyst in a reactor (nitrogen, in such a case, likely would be used to protect the catalyst from being damaged or contaminated by oxygen or moisture) it is particularly applicable when an area recently has been purged with nitrogen or carbon dioxide or some other gas and the area has been brought to the minimum safe breathing level of 19.5 percent oxygen.

Implement a Rescue System

The issue of rescue presents a particularly vexing problem when it comes to workers in nitrogen-enriched confined spaces. Because nitrogen as well as other odorless, colorless gasses is a silent killer, a worker who sees his co-worker lying on the floor of a nitrogen-enriched confined space might think the co-worker was the victim of a fall, a heart attack or some event unrelated to nitrogen asphyxiation. When human instinct kicks in and the worker attempts to save his fallen co-worker, the rescuer often becomes the second victim.

Training

Training is the glue that is necessary to bring these good practices together and make them part of an effective nitrogen-enriched confined space safety program. Workers should be trained on the use of ventilation systems, retrieval systems and atmospheric monitoring systems; hazard communication; mandatory safety practices for entry into confined spaces (such as providing ventilation and an attendant); precautions when working around equipment that may contain elevated levels of nitrogen; the reason for special fittings on compressed gas cylinders; proper use of air supply equipment; and the hazards of nitrogen-enriched atmospheres.