Choosing a Spec

Choosing a Spec

Why a Breathing Air Specification may not be the Right Choice

Compressed air is a critical utility used in over 90% of manufacturing facilities. Compressed air used for industrial purposes is in a different category from compressed air used for medical and breathing purposes. You would think that limits for breathing air would be more stringent than manufacturing air – but that’s not the case.

Breathing air specifications are primarily concerned with gases like carbon monoxide (the silent killer), carbon dioxide, oxygen percentage, total gaseous hydrocarbons, water in some cases, and condensed hydrocarbons (oil mist). The limits for breathing air are generally not adequate for process air that needs to be clean, dry and oil free.

The primary contaminants for air used in industrial applications are Particles, Water, Oil, and in some cases – Microorganisms and Gases. ISO 8573-1 Purity Classes provide acceptable limits for a variety of applications ranging from clean, dry, and oil-free to general purpose air used for industrial tools and pneumatic-fluid power-operated machines. ISO 8573-1:2010 Purity Classes are aligned with currently available purification filters. Compressed air testing is the only way to know if your purification filters are performing as expected.

ISO 8573-1 provides definitions that are key to understanding why breathing air specifications may be inappropriate for industrial / manufacturing compressed air quality.

  • Oil: a mixture of hydrocarbons composed of six or more carbon atoms (C6+).
  • Aerosol: suspension in a gaseous medium of solid particles, liquid particles or solid and liquid particles having negligible fall-velocity/settling-velocity.
  • Wall Flow: that proportion of liquid contamination no longer suspended within the air flow of the pipe.

Some breathing air specifications (but not all) include Total Volatile Hydrocarbons (sometime called gaseous hydrocarbons) and all include Condensed Hydrocarbons (sometimes called oil mist or oil aerosol). The limit for Condensed Hydrocarbons or oil aerosol in breathing air ranges from 2 mg/m3 to 5 mg/m3 (apx 2 ppm – 4 ppm).

The typical laboratory analysis for Total Volatile Hydrocarbons for breathing air is an analysis for hydrocarbons composed of one to ten carbon atoms (C1 – C10). Breathing air specifications typically allow 25 ppm or do not include a limit at all whereas ISO 8573-1 Class 1 for oil which includes the combined total of both Oil Aerosol and Oil Vapor allows no more than 0.008 ppm (0.01 mg/m3) for Class 1 – the most frequently requested Purity Class for oil in critical manufacturing applications. The analysis of Oil Vapor per ISO 8573-5 calls for the analysis of hydrocarbons composed of six of more carbon atoms (typically a range of C6 – C50).

Reasons why Breathing Air Specs are not appropriate for Critical Air Processes

  • Analysis for Total Volatile Hydrocarbons (C1 – C10) will not include common hydrocarbons that can affect your process or operation
  • Particles are not determined by size and quantity
  • Dew Point reported at atmospheric conditions instead of Pressure Dew Point
  • Breathing Air Gases (O2, CO, CO2) typically do not have a detrimental affect to products

Below is a comparison of common breathing air specifications and the typical ISO Purity Classes used for critical applications.

Limiting Characteristics CGA NFPA ISO 8573-1:2010
Grade D (SCBA) Grade E (SCUBA) 1989 (SCBA) Class 1 Class 2 Class 3
Carbon Dioxide, ppm (v/v) ≤ 1000 ≤ 1000 ≤ 1000
Carbon Monoxide, ppm (v/v) ≤ 10 ≤ 10 ≤ 5
Oxygen, % balance predominantly Nitrogen 19.5-23.5 20-22 19.5-23.5
Particles, 0.1-0.5 microns ≤ 20,000 ≤ 400,000
Particles, 0.5-1.0 microns ≤ 400 ≤ 6,000 ≤ 90,000
Particles, 1.0-5.0 microns ≤ 10 ≤ 100 ≤ 1,000
Water, ppm ≤ 24 ≤ 24
Water, Dew Point °F at 1 ATM Abs ≤ -65 ≤ -65
Pressure Dew Point, °F ≤ -94 ≤ -40 ≤ -4
Oil (Condensed) (mg/m3 at NTP) ≤ 5 (3.9 ppm) ≤ 5 (3.9 ppm) ≤ 2 (1.56 ppm)
Total Hydrocarbon Content, ppm ≤ 25 ≤ 25
Oil Aerosol and Vapor, mg/m3 ≤ 0.01 (0.008 ppm) ≤ 0.1 (0.08 ppm) ≤ 1.0 (0.8 ppm)

If you don’t find the air quality limits your company needs in ISO 8573-1, contact us with your custom specifications. We will be glad to provide a quote for analysis.

Having difficulty understanding it all? No worries – our team of experts is available to discuss the use of your compressed air and typical standards used in your specific industry. Contact us for more information about compressed air and gas testing.


To see manufacturing and ISO compressed air testing, click here to watch Videos on Air Testing with AirCheck Kit™ K8573.

About the Laboratory

Trace Analytics, LLC is an A2LA Accredited Laboratory in compliance with ISO 17025 as required by BRC and SQF. We do one thing: test compressed air! We have a great Team of Experts ready to answer your questions and help you get started with your air quality assurance program.

Process Air Industries We Serve:

Is there a problem with this page? Help us fix it - Report a Bug
Please note: We will be closed on Monday, May 29 in observance of Memorial Day.