One of the two MAIN risks of Nitrogen, asphyxiation (suffocation), cryogenic (hypothermia or frostbite) and high pressure hazards associated with handling and working with both gaseous and liquid Nitrogen. Nitrogen is a chemical element with symbol N and atomic number 7. It was first discovered and isolated by Scottish physician Daniel Rutherford in 1772.
Nitrogen asphyxiation hazards resulted in 80 deaths and 50 injuries and many of these incidents were caused by inadequate knowledge of Nitrogen hazards. The majority of incidents occurred during work in or near confined spaces, often because a person exposed to an oxygen deficient atmosphere has no warning, and cannot immediately sense that the oxygen level is too low.
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.
Typical sources for nitrogen high or low pressure gas delivered by pipeline or supplied in pressurized bottles. Nitrogen can also be delivered or supplied in liquid form.
In the oil and gas industry Nitrogen is used for:
Purging air or flammable or toxic gases from systems, Pressure testing, Leak testing, Pad pressure for offloading tank trucks, atmospheric tanks and new equipment.
Note: any use of nitrogen must be fully communicated to any workers before they work with or around it, during the hazard assessment.
In the oil and gas industry sector, nitrogen is used widely because of its “inert” properties (i.e., it does not react with or affect other material). Nitrogen is frequently used to “inert” potentially explosive atmospheres. It is often used to keep material free of contaminants, including oxygen, which can corrode equipment or present a fire and explosion hazard when in contact with flammable liquids or combustible solids, in such cases, a flow of nitrogen is maintained in a vessel to keep oxygen out.
Nitrogen is also used to purge air from equipment prior to introducing material, or to purge flammable or toxic material prior to opening equipment for maintenance. By displacing oxygen, which is necessary for combustion, the addition of nitrogen to potentially explosive or flammable atmospheres prevents the conditions by which explosion and fire can occur.
Properties of Nitrogen:
· Colorless and odourless – therefore the normal senses of sight and smell are not useful in detecting it.
· Slightly lighter than air and will tend to raise or fill a space exposed to it.
· Keep in mind that nitrogen has no “warning” properties.
Nitrogen safety, 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 odorless, 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. A breeze higher than 5 miles or death can occur with little warning.
Remember that only oxygen supports life, so if its levels dip below 21%, breathing problems occur. An atmosphere of less than 19.5% oxygen is considered hazardous. Loss of consciousness can occur after one or two breaths of nitrogen enriched atmosphere.
Note that Nitrogen is safe to breathe only when mixed with the appropriate amount of oxygen. What is Nitrogen? Nitrogen can be found in both natural and industrial settings. Causes of the incidents include personnel:
· Not knowing they were entering oxygen depleted environment.
· Not knowing the atmosphere in the environment had changed.
· Mistaking nitrogen with breathing air (workers have improperly adapted breathing apparatus fittings to fit on bottles containing pure nitrogen – a deadly mistake)
· Keep in mind that it is the lack of oxygen that causes nitrogen asphyxiation.
· Confined and enclosed spaces pose the greatest risk, including: reactor vessels, venting points within the plant, tank interiors, small rooms or enclosed buildings. These areas allow nitrogen to accumulate, creating potential for an oxygen deficient atmosphere.
· In some cases, lack of oxygen or nitrogen rich atmospheres may be detected with a personal (i.e., 4 head) monitor. It is important to note that in atmospheres that have been “inerted” using nitrogen, a standard “personal” monitor may not work.
· Most importantly, the LEL (Lower Explosive Limit) sensor, in particular, will not function in an oxygen deficient atmosphere. The monitor may give you a false reading because the sensors require a certain percentage of oxygen to function. This is something extremely important we must watch for in the vessel prior to assigning task to worker in the affected area. Be sure to contact your local safety personnel or occupational hygienist for specialized equipment which may be required for testing in “inert” atmospheres.
· In order to safely transport nitrogen, it is transported in a compressed form in cylinders (1 ft of liquid nitrogen will expand and create 696ft of gaseous nitrogen). The cylinders must be handled with care. Cylinders can “rupture” if not handled with care and become projectiles.
· Please note that contact with liquid nitrogen can readily cause frostbite. Use extreme caution when handling. You must have face, eye, hand and skin protection.