1. Death by nitrogen
Every year people die in nitrogen rich/oxygen deficient atmospheres because of ignorance, attitude and failure to adhere to safe work practices.

2. N2 vs O2 Nitrogen itself is not toxic – it exists in air at 78%.
O2 in the air is typically 20.8%
When nitrogen concentration increases, oxygen concentration decreases.
Nitrogen kills by oxygen depletion.
Note: any compressed gas can also decrease O2 concentration in an enclosed space by replacing O2.

3. Facts & Figures -Liquid nitrogen
One litre liquid gives 700 litres of gas
Nitrogen is heavier than air so accumulates at ground level.
When liquid N2 is exposed to air the cloudy vapour that you see is condensed moisture, not N2 gas. N2 gas is invisible.
OHSA recommend at least 6 changes of air per hour when using liquid N2.
Other risks: pressure, frost, confuse LEL detectors.

4. Definitions
Osmosis: If you have a concentrated mixture on one side of a permeable membrane and a dilute mixture on the other, the flow of material will be from concentrated to the dilute side.
Hypoxia : reduction of O2 supply to the tissues
Anoxia: lack of O2 supply to the tissues.

5. Transport of oxygen

6. Oxygen Osmosis
O2 flows from high concentration to low concentration.
O2 flows from high concentration to low concentration.
Concentration of O2 in the lungs is high
Concentration of O2 in the tissues and Brain is lower.
Oxygen is transported from the lungs to cells, tissue and brain via Osmosis.

7. What happens when you breathe in nitrogen?
O2 flows from high concentration to low concentration.
O2 deficient air is inhaled
Concentration of O2 in the tissues and Brain is higher than the lungs
Concentration of O2 equalises throughout the body.
O2 flows from high concentration to low concentration.
O2 deficient air is inhaled
Concentration of O2 in the tissues and Brain is higher than the lungs
Concentration of O2 equalises throughout the body.
O2 flows from high concentration to low concentration.
O2 deficient air is inhaled
Concentration of O2 in the tissues and Brain is higher than the lungs
Concentration of O2 equalises throughout the body.
Reverse Osmosis
Lungs take O2 from the blood stream which in turn takes it from the brain.

8. What happens when you breathe in nitrogen?
Brain becomes starved of oxygen – you pass out
It only takes one breath!

9. Physiological effects
Oxygen (%vol)
Effects & Symptoms
23.5
Maximum “Safe Level” OSHA 21
O2 level in air
19.5
Minimum permissible O2 level
15-19
First signs of hypoxia. Decreased ability to work strenuously. May induce early symptoms in persons with coronary, pulmonary or circulatory problems.
12-14
Respiration increases with exertion, pulse up, impaired muscular coordination, perception & judgement.
10-12
Respiration further increases in rate & depth, poor judgement, lips blue.
8-10
Mental failure, fainting, unconsciousness, ashen face, blueness of lips, nausea, vomiting, inability to move freely.
6-8
8 minutes – 100% fatal
6 minutes – 50% probably fatality rate
4-6
Coma in 40 seconds, convulsions, respiration ceases, death

10. How long does it take to have an effect?
When a person enters an oxygen deprived atmosphere the oxygen level in the arterial blood drops to a low level within 5-7 seconds.
Loss of consciousness follows in seconds.
Heart failure and death ensue if person does not receive any oxygen in 2-4 minutes.

11. What If I hold my breath?
Holding your breath causes the oxygen in your blood to be used up. If you then inhale the inert atmosphere, suffocation and death will follow in most cases (INRS ED 632)

12. Do I have to be in an enclosed space to be at risk?
No. Any situation where you can breathe oxygen deficient air has the same effect.
Incident at Texas City where individual was working on top of reactor. He leaned over, got a blast of pure N2 and pitched forward into the vessel unconscious.
When cold, Nitrogen is more dense than air so lower concentration at floor level. If you lean down into a liquid nitrogen spillage you are also at risk.

13. What if I see a colleague who is unconscious?
Call emergency services.
Do not enter the area without self contained breathing apparatus.
Over 50% of workers who die in confined spaces are attempting to rescue other workers.

14. What about Helium?
Helium is much less soluble in water than many other gases, such as nitrogen.  The low solubility means it does not enter the blood stream, even under pressures commonly experienced by deep sea divers

15. Why is He added to SCUBA tanks?
Under water, a scuba diver is subjected to added pressure, up to 10 times normal atmospheric pressure at a depth of 300 feet.  Under these conditions, greater amounts of oxygen enter into the bloodstream.  If the concentration becomes too high, oxygen poisoning can result, with symptoms that include confusion, impaired vision and nausea.  So, under high pressures, oxygen must be diluted with some other gas, usually helium.

16. Why isn’t N2 added to SCUBA tanks?
Nitrogen is much more soluble in water than Helium. At the elevated pressures experienced by divers, larger amounts of nitrogen will dissolve in the blood causing nitrogen narcosis.  Dissolved nitrogen also can cause a painful condition, called "the bends" if a diver makes too rapid an ascent.  As the pressure decreases, the dissolved gas can form bubbles that can stop circulation in capillaries and damage the nervous system.

17. What about inhaling helium from balloons?
A popular party trick is to inhale helium from a helium filled balloon and talk like Mickey Mouse.
Sound is produced by our vocal cords through vibration. The air around our vocal cords is vibrated,and we interpret this as sound. Helium is a much lighter gas than air , allowing the vocal cords to vibrate much faster, giving a high pitch voice. As the helium is replaced by regular air the voice returns to normal.

18. So it’s safe to inhale Helium?
NO!! Breathing in any O2 deficient gas or air will cause hypoxia.
Many people have suffered hypoxia by inhaling helium from balloons at parties, and some have even died after inhaling the entire contents of a balloon.
Even more dangerous are compressed He bottles which are now available to the pubic for party balloons. People are dying from aneurisms after inhaling He from a pressurised container while attempting party tricks.
BOC are campaigning to restrict the availability of helium to the general public to prevent further fatalities.