Because of its inert nature, gaseous nitrogen is widely used for various purging, blanketing, and flushing operations. Depending on the type of process involved, different levels of nitrogen purity are required to meet specific manufacturing needs.
What Is Nitrogen Purity?
Nitrogen purity refers to the proportion of nitrogen present in a sample compared with the impurities it contains. Based on the ratio of pure nitrogen to contaminants such as oxygen, water vapor, carbon monoxide, and carbon dioxide, nitrogen can be classified as either high-purity or low-purity.
This classification, determined by nitrogen concentration, plays a key role in evaluating the suitability of nitrogen for any industrial application.
High-Purity vs. Low-Purity Nitrogen
The purity of a nitrogen sample is defined by the percentage or concentration of pure nitrogen it contains. To be considered high-purity, the gas must contain at least 99.998% nitrogen, while lower-purity nitrogen typically has a higher proportion of impurities.
High-Purity Nitrogen
Nitrogen gas with a concentration above 99.998% is considered high-purity. Although different manufacturers may use slightly different standards, high-purity nitrogen is generally classified as “zero grade”. This designation means the gas contains less than 0.5 ppm of hydrocarbon impurities.
Key characteristics of high-purity nitrogen include:
- Oxygen concentration ≤ 0.5 ppm
- Carbon monoxide/carbon dioxide ≤ 1.0 ppm
- Moisture ≤ 3 ppm
Low-Purity Nitrogen
Nitrogen with a concentration between 90% and just below 99.9% is considered low-purity.
Nitrogen Purity Grading System
Nitrogen is classified using a numerical grading system that indicates its minimum purity level. The first digit represents the number of nines, while the second digit represents the digit following the last nine.
The main purity grades include N2.0, N3.0, N4.0, N5.0, N6.0, and N7.0.
What Is Ultra High Purity Nitrogen?
Ultra High Purity (UHP) Nitrogen refers to nitrogen with a concentration of 99.999%, where impurities are negligible. Its specifications are strict, and any variation can invalidate the classification.
For UHP nitrogen:
- Oxygen content must not exceed 2 ppmv
- Total hydrocarbons ≤ 0.5 ppmv
- Moisture ≤ 1 ppmv
Ultra high purity nitrogen is primarily used in scientific and high-tech applications.
Nitrogen Purity Grades Comparison
| Grade | Purity (%) | Impurities (ppm) | Typical Use |
|---|---|---|---|
| N2.0 | 99.0 | 10,000 | General industrial use, inerting |
| N3.0 | 99.9 | 1,000 | Welding, purging, pressure testing |
| N4.0 | 99.99 | 100 | Food packaging, general electronics |
| N5.0 | 99.999 | 10 | Semiconductor, lab analysis |
| N6.0 | 99.9999 | 1 | Semiconductor manufacturing, high-end R&D |
| N7.0 | 99.99999 | 0.1 | Ultra-clean processes, aerospace applications |
What Is Oxygen-Free Nitrogen?
Oxygen-Free Nitrogen (OFN) is defined as nitrogen gas containing no more than 0.5 ppm of oxygen. The purity of OFN typically remains at 99.998%. This type of nitrogen is often used in scientific research and calibration processes where even trace oxygen impurities could alter results or cause inaccuracies.
Nitrogen Purity by Industry and Application
As mentioned, the required nitrogen purity varies significantly across industries. The key factor when selecting a grade is how impurities may affect the intended application. Sensitivity to moisture, oxygen, and other contaminants must be carefully considered.
Food-Grade / Beverage-Grade Nitrogen
Nitrogen is widely used in food and beverage production, packaging, and storage. In these applications, nitrogen helps preserve shelf life by eliminating oxidizing agents, maintaining flavor, and preventing rancidity. Food-grade nitrogen generally requires a purity level between 98% and 99.5%.
Pharmaceutical-Grade Nitrogen
Pharmaceutical manufacturing demands high-purity nitrogen to prevent contamination or alteration of final products. Many drug production processes require nitrogen with purities ranging from 97% to 99.99%. High- and ultra-high-purity nitrogen are used for tank blanketing, equipment purging, and packaging to maintain freshness and protect active ingredients from degradation.
Oil and Gas Applications
Nitrogen with a purity of 95–99% is commonly used in the oil and gas industry to reduce the risk of fire and explosion. It is also used for tank inerting, pipeline purging, and pressure testing during maintenance or decommissioning operations.
Nitrogen Purity by Industry and Application
Different industries require different levels of nitrogen purity depending on process sensitivity to oxygen, moisture, and other contaminants.
| Industry / Application | Typical Purity (%) | Purpose |
|---|---|---|
| Food & Beverage | 98–99.5 | Preserve freshness, prevent oxidation |
| Pharmaceutical | 97–99.99 | Prevent contamination, storage blanketing |
| Oil & Gas | 95–99 | Reduce explosion/fire risks, pipeline purging |
| Semiconductor & Electronics | 99.999–99.9999 | Process protection, carrier gas, cleanroom environment |
| Metal Processing | 95–99.999 | Heat treatment, laser cutting |
| Power Generation | 95–99.6 | Purging, sealing, boiler maintenance |
| Plastic Manufacturing | 95–99.5 | Injection molding, extrusion |
Uses of Ultra High Purity Nitrogen
Ultra high purity nitrogen serves as a protective and carrier gas in the production of integrated circuits, semiconductors, and vacuum electronic devices. It is used as a carrier gas during Chemical Vapor Deposition (CVD), for liquid diffusion source transport, and as a protective atmosphere in high-temperature diffusion furnaces.
In epitaxy, lithography, cleaning, and evaporation processes, UHP nitrogen is used for purging, drying, storage, and gas transport. For cathode-ray tube manufacturing, nitrogen purity must exceed 99.99%. In aerospace technology, UHP nitrogen is essential for purging liquid hydrogen fueling systems before and after filling operations.
Production of High-Purity Nitrogen
The preparation of high-purity nitrogen mainly relies on air separation technology. First, compressed air is separated to isolate nitrogen from oxygen and other impurities. Advanced purification methods such as cryogenic distillation, pressure swing adsorption (PSA), and membrane separation are then used to remove trace contaminants.
These techniques ensure the high quality and stability of nitrogen, providing a reliable gas supply for industrial and scientific use.
Applications of High-Purity Nitrogen
Due to its exceptional purity and stability, high-purity nitrogen plays an important role across numerous sectors.
- Industrial Production: Used in metallurgy, chemical synthesis, and electronics manufacturing to enhance product quality and efficiency.
- Scientific Research: Provides a clean gas environment to ensure the accuracy of experimental results.
- Medical and Aerospace Fields: Essential for precision operations and safety-critical applications.
Plastic Manufacturing Grade Nitrogen
Nitrogen used in plastic manufacturing typically requires:
- 95–98% purity for standard injection molding
- 99.5% purity for gas-assisted injection molding
- 98–99.5% purity for film-blowing and extrusion processes
Metal Processing Grade Nitrogen
In metal processing, nitrogen purity requirements vary widely — from 95–99% for heat treatment to 99–99.999% for laser cutting operations.
Power Generation Grade Nitrogen
In power generation, nitrogen with a purity of 95–99.6% is used for seal purging, boiler laying-up, gas pipeline purging, and water softening system blanketing.
About JinHong Gas
As a leading industrial gas supplier, JinHong Gas provides a full range of nitrogen products — from standard industrial nitrogen to high-purity and ultra high purity grades. With advanced air separation and purification technologies, JinHong ensures stable quality, precise purity control, and reliable delivery for industries such as semiconductors, pharmaceuticals, food processing, and aerospace.
Our technical expertise and customized solutions help clients optimize performance, reduce operational risks, and achieve higher production efficiency. Whether for laboratory research or high-volume industrial applications, JinHong Gas is your trusted partner for safe, consistent, and high-quality nitrogen supply.
