Last year I was attending some continuing education for my hazardous materials work. The instructor was outstanding until he went on his tirade against Nitrogen (N2). He was factually correct when he stated that N2 was a leading killer within confined spaces, but he went off the rails when he tried to convince me that N2 is a toxic hazard and it is this toxic hazard that is killing workers. So I looked around the room and there was one or two others who were looking around the room like what the h_ll am I hearing. So being me, I had to ask the question… So what is the PEL/TLV for N2? What is the IDLH of N2? (for the non-members, this is a TRICK question!)
There are NO exposure limits for N2. In fact, every breath we take is 78% Nitrogen. N2 is a SIMPLE ASPHYXIANT which is defined as:
a substance or mixture that displaces oxygen in the ambient atmosphere, and can thus cause oxygen deprivation in those who are exposed, leading to unconsciousness and death.
N2 is NOT a toxic hazard, it’s hazard lies in the fact that it is a SIMPLE ASPHYXIANT. Here is OSHA’s explanation of a Simple Asphyxiants:
VII.11 Simple Asphyxiants Introduction
An asphyxiant is a vapor or gas that can cause unconsciousness or death by suffocation due to lack of oxygen. Asphyxiants can be either chemical asphyxiants or simple asphyxiants.
Chemical asphyxiants cause suffocation by either preventing the uptake of oxygen in the blood or by preventing the normal oxygen transfer from the blood to the tissues or within the cell itself.
Simple asphyxiants are inert gases or vapors which are harmful to the body when they become so concentrated that they reduce oxygen in the air (normally about 21 percent) to dangerous levels (19.5 percent or less). When the concentration of a particular gas increases, the fraction of inspired oxygen decreases, causing decreased oxygen in the blood. A decrease in the fraction of inspired oxygen to less than 19.5% causes inadequate oxygen supply within minutes after exposure to a simple asphyxiant and may result in unconsciousness or death. Asphyxiation is a well-known hazard in the workplace. Simple asphyxiants frequently contribute to industrial accidents involving loss of life and are of particular concern for those who work in confined spaces, as these gases are colorless and odorless and offer no warning properties.
Definition and General Considerations
Simple asphyxiant means substance or mixture that displaces oxygen in the ambient atmosphere and can thus cause oxygen deprivation in those who are exposed, leading to unconsciousness and death. Simple asphyxiants are of particular concern in enclosed spaces. Some examples of simple asphyxiants include nitrogen, helium, neon, argon, krypton, and xenon. These gases are well-known simple asphyxiants from experience in the workplace. Evaluation of other gases as simple asphyxiants requires expert judgment to evaluate evidence such as human experience, information from similar substances, and other pertinent data.
