What Is Nitrogen Purity?

One of the most common questions we receive while working with clients is “what nitrogen purity do I need?”, and it’s one of the most important items to correctly identify. Each application will require a unique purity level, depending on its tolerance for oxygen.

When speaking about nitrogen, the term purity refers to the level of gas concentration. Nitrogen is one of the most plentiful elements in our galaxy and accounts for 78% of the air that we breathe. The remaining 22% is comprised of oxygen (~21%) and trace gases (~1%). When you begin to eliminate the oxygen and trace gas, you increase your nitrogen concentration, or purity.

A common misconception when discussing nitrogen purity, is that it refers to the presence of contaminants, such as particulate matter and oil vapour. While filtering these contaminants is highly critical, it should not be confused for purity when speaking about nitrogen. Nitrogen is inherently a very dry and clean gas and whether acquiring it in bulk liquid, pressurized cylinder, or through on-site generation, it has a low dew point and should be supplied clean of contamination.

Why Is Identifying Nitrogen Purity Important?

Correctly identifying the nitrogen purity that your process requires is very important. Over specifying the purity will result in a wasteful and expensive ordeal, while under specifying the purity will overexpose the process to oxygen and potentially compromise the finished product. Each industry, application and process will require varying purity levels, depending on the immediate and long term sensitivity to oxygen. Understanding how much oxygen your process can tolerate and engineering a solution to deliver a customized purity will result in financial gain.

Typical Nitrogen Purity by Industry

How and when Is Purity Analyzed?

Bulk Liquid & Pressurized Cylinder

When purchasing nitrogen in bulk liquid or pressurized cylinder, the gas is analyzed at the air separation plant and typically supplied at 99.999%, regardless of the application. Following analysis, the gas is stored, transported, decanted, then used. From generation to delivery, the gas is introduced to various connection points, hoses and storage vessels before it is released to the final process. For applications which only require 95% nitrogen purity, traditional supply can be wasteful if there is no benefit to increasing the concentration level.

On-Site Gas Generation

On-site nitrogen generation systems are engineered to deliver gas at the optimum purity prescribed for the application, resulting in increased efficiency and dollars saved. When producing nitrogen through on-site generation, purity is analyzed directly at the point of generation, moments before it enters the distribution network of pipe within the facility. Purity is analyzed using an internal oxygen sensor which displays the gas concentration in real time. The controls within the gas generator are configured to never allow purity never to fall below a prescribed set point. The end result is cost effective N2 supply, without the diminishing return associated with purchasing unnecessarily high purity gas.


Purity can be analyzed as a percentage of nitrogen concentration, or in PPM (parts per million) of the remaining oxygen content. The analysis and identification format will often be a result of how ‘pure’ the nitrogen needs to be. Typically, purity levels of 99.9% and below will be analyzed as a percentage of concentration, due to precision being less critical. Purity levels of 99.95% and above will be measured in PPM of remaining oxygen content, providing a higher resolution of analysis.


  • 99.0% purity will be identified and displayed as such; 99% nitrogen, or 1% oxygen content remaining.

  • 99.995% purity will be identified and displayed as 50 PPM; the remaining oxygen in parts per million.

Need Help?

Developing custom nitrogen purity solutions is our competency.

  • Our engineering team can assist in determining the most suitable purity for your process and provide a solution engineered for your applications.

  • Our field service team can provide a real time purity assessment using calibrated oxygen analyzing equipment. Testing is completed at your facility and directly at your process. Just because you are purchasing nitrogen at 99.999%, it doesn’t mean that your process is receiving it.

  • Our parts team can provide custom gas mixes for field testing varying purity levels, ensuring optimum purity efficiency and maximum dollars saved.