Introduction
When sourcing high purity gases, one of the most common questions engineers and procurement managers ask is: "What purity level do I actually need?" The answer depends on your application — and choosing the wrong grade can either compromise your process or cost you more than necessary.
This guide explains the difference between 4N, 5N, and 6N purity grades and helps you determine which is right for your application.
Understanding the "N" Purity Scale
The "N" in gas purity stands for the number of nines in the purity percentage:
- 4N = 99.99% pure (100 ppm total impurities)
- 5N = 99.999% pure (10 ppm total impurities)
- 6N = 99.9999% pure (1 ppm total impurities)
Each step up represents a 10x reduction in impurity levels — and typically a significant increase in cost.
4N Purity — When Is It Enough?
4N (99.99%) grade gases are suitable for many industrial and general laboratory applications. Common uses include:
- General laboratory analysis
- Carrier gases for non-critical chromatography
- Industrial process gases where tight purity specs are not required
5N Purity — The Most Common Choice for Electronics
5N (99.999%) is the workhorse purity grade for most electronic and semiconductor applications. Typical applications include:
- LED manufacturing (MOCVD processes)
- Solar cell deposition
- Semiconductor etching and CVD
- Research and development laboratories
6N Purity — For the Most Demanding Applications
6N (99.9999%) gases are reserved for the most critical processes. These include:
- Advanced semiconductor fabrication (logic chips, memory)
- Quantum computing research
- Precision optical coatings
- Ultra-sensitive analytical instruments
How to Choose the Right Purity Grade
- What are the impurity tolerance limits in your process recipe?
- What does your equipment manufacturer recommend?
- What are the consequences of contamination in your process?
- What is your budget for gas supply?
When in doubt, consult with your gas supplier's technical team. Over-specifying purity wastes money; under-specifying risks process failures.
Conclusion
Understanding the 4N vs 5N vs 6N distinction is fundamental to smart gas procurement. NextPure offers all three grades with full traceability and Certificates of Analysis. Contact us to discuss which purity level is right for your application.