Oxygen Compatible Air (OCA): Comprehensive Specifications and Analysis

Oxygen Compatible Air (OCA) is essential for safety and performance in systems utilizing high concentrations of oxygen. However, determining the correct specifications can be challenging due to varying standards and interpretations. At Analytical Chemists Inc., we aim to clarify these complexities with scientifically grounded guidelines.

Common Standards for Oxygen Compatible Air OCA

Several leading organizations provide specifications for OCA, including:

• AAUS (American Academy of Underwater Sciences)
• ANDI (American Nitrox Divers International)
• IANTD (International Association of Nitrox and Technical Divers)
• U.S. Navy

These standards generally agree on maintaining condensable hydrocarbon levels below 0.1 mg/m³, yet discrepancies arise regarding particulate requirements.

The Challenge with Particulate Standards

Expecting an air sample from dive shop piping to meet particulate limits of less than 2 microns is not only impractical but unsupported by empirical evidence.

• Unrealistic Expectations: The 2-micron particulate specification surpasses even the criteria for a Class 100 cleanroom—a standard for environments requiring ultra-clean air.
• Global Benchmarks: NASA, the global authority on oxygen systems, adheres to less stringent particulate specifications for its oxygen-handling equipment.

Our Approach to Oxygen Compatible Air Standards

We have developed a scientifically robust and achievable specification for OCA. This standard incorporates:

1. Existing Industry Specifications: Building on guidelines from AAUS, ANDI, IANTD, and the U.S. Navy.
2. NASA Oxygen Handling Criteria: Leveraging NASA’s proven standards to ensure safety and reliability.
3. Realistic Sampling Techniques: Factoring in the practical limitations of current sampling and analytical technologies.

Draft Specification for Oxygen Compatible Air

This draft OCA specification balances stringent safety requirements with practical application:

• Condensable Hydrocarbons: ≤ 0.1 mg/m³
• Particulate Levels: A realistic threshold that reflects achievable conditions in commercial and industrial environments.
• Rationale for Peer Review: Each element of the specification is supported by experimental data, engineering expertise, and field-tested methodologies.

The Importance of Rational Specifications

Establishing realistic and scientifically backed specifications for OCA ensures:

• Enhanced Safety: Preventing combustion risks associated with oxygen-rich systems.
• Practical Compliance: Enabling dive shops, industrial facilities, and medical applications to meet standards without undue burden.
• Confidence in Testing: Providing accurate results based on achievable sampling conditions.

Collaborate with Analytical Chemists Inc.

As industry leaders in Oxygen Compatible Air analysis, we invite peer review and input to refine our specifications further. Our goal is to create standards that prioritize safety, practicality, and technological feasibility.

For expert analysis of your OCA systems, contact Analytical Chemists Inc. today at (888) 724-7522.

Your trusted partner in air quality and safety.

Option & Rationale for the Proposed Draft Version for Oxygen Compatible Air (OCA)

At Analytical Chemists Inc., we approach the specifications for Oxygen Compatible Air (OCA) with a balance of scientific evidence, industry standards, and practical experience. Below is a detailed rationale for the criteria included in our draft version, designed to meet the needs of OCA applications while maintaining precision and safety.

Carbon Dioxide (CO₂): 1000 ppmv

• Reasoning: While some OCA standards revert to the previous limit of 500 ppm, we find no supporting data to justify this change. We retain the CGA Grade E criterion of 1000 ppm, based on real-world observations.
• Indicator Value: Elevated CO₂ levels in compressor air signal saturated chemical filters. Although we monitor levels exceeding 800 ppm as a warning, we only recommend corrective action when the levels rise significantly higher.

Carbon Monoxide (CO): 2 ppmv

• Reasoning: Although this limit may appear overly stringent, we align with the prevailing industry consensus to ensure credibility and widespread acceptance.

Condensable Hydrocarbons: 0.1 mg/m³

• Reasoning: This value is reasonable, as hydrocarbons can accumulate over time. Keeping this threshold ensures the long-term safety of oxygen systems.

Total Volatile Hydrocarbons (Including Methane): 15 ppmv

• Reasoning: Levels exceeding 15 ppm are rare and warrant investigation. By setting this threshold, we proactively address potential hazards while avoiding complacency associated with higher limits.

Particulate Limits: Adopting NASA Standards

Particle Count (per NASA specifications):

• 101–250 µm: ≤93 particles
• 251–300 µm: ≤3 particles
• >300 µm: 0 particles

While some specifications call for a 1 or 2-micron limit, we find no scientific evidence supporting these thresholds. Our focus remains on identifying and limiting larger particles, which are more likely to cause equipment or safety issues.

Fibers (per NASA specifications):

• 0–500 µm: ≤20 fibers
• 501–1000 µm: ≤3 fibers
• >1000 µm: 0 fibers

These values are derived from NASA’s Oxygen Cleaning Specifications, which analyze particulate and fibers in rinsate from a defined surface area. While sampling compressed gas directly differs from rinsate analysis, we employ high-velocity sampling to mimic the effectiveness of rinsate methods. This approach enhances the detection of particle clusters, which could pose ignition risks.

Laboratory Analysis for Oxygen Compatible Air

Analyzing OCA requires more precise methods compared to standard SCUBA air testing due to the heightened risks associated with oxygen-rich environments.

Challenges in OCA Analysis:

• Oil Mist and Particulate: Unlike SCUBA air, where filters are weighed pre- and post-sampling, OCA analysis must detect non-volatile hydrocarbons below 0.1 mg/m³ with greater accuracy.
• Ignition Risks: Even trace levels of sticky debris can accumulate and become ignition sources, requiring highly sensitive and reliable testing methods.
• Solid Particulate: The ignition potential of particles depends on both mass and morphology, necessitating advanced microscopy techniques for particles ≥100 µm.

Our Analytical Approach:

• Microscopy: Used for particle analysis, ensuring precision for particles 100 microns or larger.
• Hydrocarbon Measurement: Adheres to NASA protocols, surpassing the reliability of simpler gravimetric methods.

Oxygen Compatible Air Sampling Kits

To accommodate the unique demands of OCA testing, we have enhanced our Sport Diving Air Sampling Kit to double as a reliable solution for both SCUBA air and OCA testing. Key improvements include:

• Compatibility with NASA-recommended analysis methods.
• Streamlined preparation and operation for dual-purpose applications.
• Durable, efficient, and cost-effective design.

Our Oxygen Compatible Air Sampling Kits reflect a commitment to scientific rigor, operational convenience, and safety—ensuring compliance with the most demanding oxygen system standards.

For precise and reliable Oxygen Compatible Air (OCA) testing, trust Analytical Chemists Inc. Contact us today to learn more or schedule your next test.
Call Us: (888) 724-7522