Why OCA Testing Is Essential
The safe addition of oxygen to a diver’s air supply requires careful consideration of air purity. While much is known about the mechanics of oxygen blending, ensuring the air’s compatibility with oxygen involves precise analysis. At the forefront of this process is OCA testing—the analytical verification that breathing air meets stringent purity standards, particularly regarding hydrocarbons and particulate matter.
The challenge lies in the absence of a universally accepted specification for Oxygen Compatible Air (OCA). This lack of consensus has created confusion across the industry. Without a single, well-documented standard, inconsistencies arise in the sampling, testing, and reporting of OCA.
While we specialize in the sampling and analysis of breathing air systems, our expertise does not extend to oxygen blending techniques or equipment. Our focus is on ensuring your air meets the highest safety and purity standards through reliable analytical methods.
All insights and practices we share are drawn from published sources and extensive personal experience, ensuring that our OCA testing services are both analytically robust and practical.
For standard SCUBA air, there are well-defined guidelines, such as:
However, for OCA, there is no widely accepted standard. Multiple organizations have introduced their own specifications, including:
Compounding the issue, the Compressed Gas Association (CGA) does not yet provide an official OCA specification. This vacuum has led some laboratories to create their own “Modified CGA Grade E” or even “Modified CGA Grade J” standards, despite the latter being unsuitable for most air compressors. These ad hoc modifications often diverge significantly from the original specifications, creating confusion and inconsistency.
For many dive shop owners and operators, the differences between OCA specifications are poorly understood. Most rely on their chosen laboratory to define and apply appropriate standards, often selecting labs based on pricing rather than technical expertise.
This raises critical questions:
These inconsistencies make it crucial to work with a lab that offers transparent, reliable OCA testing and explains the standards being applied.
We believe there are three primary reasons to push for a single, universally accepted OCA specification:
Our clients often request testing based on existing specifications from organizations like ANDI or IANTD, but we advocate for a more unified approach. While no single specification currently serves as the industry standard, our preferred testing methods align with the most reliable and scientifically validated practices.
Inconsistent standards can lead to:
By choosing a laboratory that prioritizes consistency, transparency, and scientific rigor, you can trust that your OCA testing results truly meet the requirements for safe and effective oxygen blending.
Our comprehensive OCA testing services provide:
Don’t leave the safety of your oxygen-compatible air to chance. Contact us today to learn more about our OCA testing services and how we can support your operations with reliable, accurate results.
The table below lists the current specifications that our clients request, and one that we prefer.
When it comes to ensuring Oxygen Compatible Air (OCA) meets rigorous safety and cleanliness criteria, having a clear, practical, and effective specification is essential. Our proposed draft specification draws from industry best practices and the proven methodologies outlined in NASA’s Oxygen Safety Manual. Here’s why we stand behind our recommendations and how they address current shortcomings in the industry.
Maintaining CO₂ at or below 500 ppmv ensures the chemical filters are functioning correctly. Elevated CO₂ levels serve as an early warning that a filter is nearly spent, offering a proactive measure to prevent air quality degradation.
This limit aligns with industry standards and represents a consensus-based approach for safety. We defer to the majority opinion on this parameter.
This threshold ensures hydrocarbons remain at safe levels. It is widely regarded as reasonable, and we support the majority opinion on this criterion.
Our experience shows that volatile hydrocarbon levels exceeding 15 ppmv are unusual and often signal a deeper issue. Setting the limit at 15 ppmv encourages investigation when anomalies occur, promoting safety and system integrity. Accepting higher limits, such as 25 ppmv, risks overlooking these critical warnings.
This value mirrors NASA’s Non-Volatile Residue (NVR) standards and serves as a catch-all for cases where particulate smaller than 100 microns or discoloration appears despite low hydrocarbon levels. It provides an additional layer of safety.
These limits, adapted from NASA’s oxygen cleaning specifications, prioritize total debris over surface area considerations. This approach errs on the side of safety, ensuring that particulate contamination remains within manageable and safe thresholds.
Unlike other standards (e.g., AAUS, ANDI, IANTD), which often lack detailed particulate criteria, our draft specification is comprehensive and practical. It integrates proven guidelines from NASA while addressing the limitations of overly stringent and often impractical criteria such as the 1 and 2 micron particulate specifications.
Testing for 1 and 2 micron particles is highly time-intensive and often impractical. The process is tedious, and the margin for error during sample handling is significant. Laboratories face the temptation to cut corners, increasing the likelihood of inaccurate results.
Air sampling kits and handling protocols are vulnerable to micro-contamination:
If a sample fails due to a single 10-micron particle, it’s nearly impossible to determine whether the contamination originated from the air system, the sampling kit, or the laboratory itself.
Repeated failures due to unrealistic standards (e.g., 1–2 micron particulate limits) could drive store owners to seek alternative labs, potentially undermining trust in the testing process. This situation discourages labs from enforcing these standards rigorously, further compromising consistency and reliability.
NASA’s oxygen cleaning specifications offer a realistic, research-backed framework for OCA. These guidelines are grounded in experimental data and real-world experiences, making them more reliable than alternative industry specifications.
By adopting NASA’s proven criteria, our draft OCA specification ensures:
Our proposed OCA specification avoids the pitfalls of overly complex and impractical standards while leveraging the expertise and experience embedded in NASA’s guidelines. It prioritizes safety, feasibility, and consistency, ensuring oxygen-compatible air meets the needs of divers, store owners, and laboratories alike.
If you’re ready to transition to a more practical and effective OCA testing standard, contact us today to learn more about our services and how we can support your safety and compliance needs.
Contact our local service center if you are unable to resolve a contamination issue. Contact us if you need the name of a technical specialist located in your area.