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  • how are you sure it is safe to enter..
  • What are your precautionary measures before entry..
  • Do you carry a portable gas detector that beeps if oxygen falls below 19%..
  • Do you have a standby attendant..
  • Do you know that you can be overcome by N2 by just looking into the manhole without wearing breathing apparatus..
  • Never put your head into open connections of storage tanks, columns, flange connections etc.

Nitrogen - the invisible Killer

The atmosphere we live in, the air we breathe every day consists of 78% Nitrogen, 21% Oxygen and 1% traces of other gases. But only oxygen is vital and essential to human beings for respiration/survival. Without sufficient oxygen, i.e. if oxygen level falls below 16%, we will die of asphyxiation.


Effects and Symptoms
23.5 Maximum "Safe Level" (23% is often the High level alarm of most O2 detectors)
21 Typical O2 concentration in air
19.5 Minimum "Safe Level" (19% is often the Low level alarm of most O2 detectors)
15-19 First sign 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 and judgment
10-12 Respiration further increases in rate and depth, poor judgment, lips blue
8-10 Mental failure, fainting, unconsciousness, ashen face, blueness of lips, nausea, vomiting, inability to move freely
6-8 6 minutes - 50% probability of death, 8 minutes - 100% probability of death
4-6 Coma in 40 seconds, convulsions, respiration ceases, death

What is an Asphyxiant..

  • A chemical (gas or vapour) that can cause death or unconsciousness by suffocation.
  • Simple aphyxiants such as nitrogen, displace oxygen in air.
  • They become especially dangerous in confined or enclosed spaces.
  • Chemical asphyxiants, such as carbon monoxide and hydrogen sulfide, interfere with the body's ability to absorb or transport oxygen to the tissues.

YouTube Video
Hazards of Nitrogen Asphyxiation

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