Air Sampling Guide: Breathing Air Purity

Everything You Need to Know to Select the Best Vendor

Overview

Most retail operations that fill SCUBA and SCBA tanks maintain consistent air purity. For these businesses, air sampling and analysis might seem like a costly, routine confirmation of their systems’ reliability. However, routine air sampling and analysis serve as critical diagnostic tools, capable of identifying existing issues or potential failures before they become critical. Regular air purity checks also provide competitive advantages, ensuring customer trust and operational excellence in an increasingly discerning market.

While you may rely on a laboratory for air analysis, selecting the right vendor is a pivotal decision. Many labs offer sampling equipment and analytical services, but not all labs are equal. The quality of your lab’s services directly impacts your operations and reputation. How can you ensure the reliability of their results? This guide highlights key considerations to help you make an informed choice.

Sampling Strategy: It All Starts Here

During routine use, compressors release small amounts of debris, including desiccant, water, oil mist, and carbon monoxide. These contaminants are typically filtered out by your system. However, filter failures or specific operating conditions can allow debris to enter SCUBA or SCBA tanks, posing a significant safety risk.

To accurately detect contaminants, air sampling must replicate the flow rates experienced during tank filling. High flow rates dislodge debris adhering to pipe walls, simulating real-world conditions. Unfortunately, most labs do not sample at high flow rates, significantly limiting their ability to detect contaminants effectively. Only two labs in the U.S. provide high flow rate sampling. Sampling at low flow rates underestimates debris levels and fails to account for elevated carbon monoxide generated by compressors running hot during high-demand operations. Reliable sampling strategies must prioritize flow rate accuracy, not just pressure control.

Sampling Equipment: Key Considerations

High-pressure systems present unique challenges, particularly in controlling pressure while achieving full-flow conditions. Many commercially available sampling kits fail to address these challenges effectively:

1. Inadequate Flow Rates: Some kits rely on pinhole restrictors (∼0.018-inch diameter) to maintain full pressure, but their flow rates are too low (∼3 SCFM or 100 LPM) to reveal accurate particulate and oil mist data. These restrictors are also prone to clogging, compromising sampling reliability.
2. Pressure Regulators: Kits utilizing pressure regulators to reduce pressure and flow rates inadvertently filter out the very debris being tested. Regulators’ sintered filters and impinging surfaces trap contaminants, rendering results unreliable. Additionally, industry standards like CGA Grades D and E (ANSI S-7) explicitly prohibit pressure regulators in sampling kits.
3. Filter Size: Membrane filters are standard for capturing oil mist and particulates, but small filters (<37 mm) lack sufficient surface area. High-velocity airflow (∼13-18 SCFM) can displace captured oil, invalidating results. Filters larger than 37 mm are recommended for accurate analysis.
4. Gas Collection Media: Hydrocarbons, carbon monoxide, and carbon dioxide are typically collected in metal flasks, glass vials, or air bags. While air bags (e.g., Tedlar or aluminized Mylar) are lightweight and practical, they can permit diffusion of hydrocarbons over time. Glass vials avoid diffusion issues but are fragile and may absorb hydrocarbons through rubber seals. Metal flasks offer durability and minimal absorption, making them ideal for precise analysis.

Analysis of the Sample

Once collected, samples undergo laboratory analysis using methods such as:

• Colorimetric indicator tubes
• Gas cell infrared spectrometry
• Gas chromatography (GC)
• Gas chromatography/mass spectrometry (GC/MS)
• Analyte-specific portable meters

Unlike environmental testing, which is regulated by the EPA, compressed breathing air analysis lacks a governing oversight agency. Certification from organizations like AIHA or A2LA provides general quality assurance but does not guarantee reliable results for compressor air analysis. Understanding the laboratory’s methods and their adherence to industry best practices is crucial.

Elements of a Robust QA Program

The ultimate assurance of air purity lies in a well-implemented Quality Assurance (QA) program. While most dive store owners claim to have QA systems in place, the effectiveness of these programs varies widely. Comprehensive QA programs must include periodic air analysis conducted by a reputable laboratory. This is not merely an expense but an investment in operational integrity and client safety.

Key elements of a strong QA program include:

• Regular preventative maintenance of hardware
• Routine air purity analysis
• Adherence to established purity specifications, such as CGA Grades D and E

Diving organizations like PADI, NAUI, and SSI, as well as OSHA guidelines, emphasize the importance of routine air quality checks. Though recreational diving air supplies are not federally regulated, the U.S. Navy and other leading organizations set a high standard by requiring CGA Grade D or better.

Specifications and Standards

Divers place implicit trust in the quality of breathing air provided by their local dive shops. This trust is contingent upon adherence to rigorous purity standards. A well-informed approach to air sampling and analysis not only ensures compliance with these standards but also reinforces customer confidence.

By selecting the right laboratory and implementing a robust QA program, you protect your clients and your reputation. At Analytical Chemists, Inc., we’re here to guide you through this process with unparalleled expertise and reliable solutions. Contact us today to learn how we can support your air sampling and analysis needs.