Is all breathing air created equal? Not when safety is on the line. That’s why the Compressed Gas Association (CGA) developed the grading system that many organizations adhere to today for compressed breathing air.
Understanding the difference between Grade E and Grade D air and other regulatory requirements is essential for fire departments, dive shops, industrial EHS teams, and anyone who relies on compressed breathing air for their operations.
This guide breaks down:
The CGA developed standardized breathing air grades to ensure that compressed air used in Self-Contained Breathing Apparatus (SCBA) and Self-Contained Underwater Breathing Apparatus (SCUBA) is safe.
First published in 1966 (CGA G-7.1 Commodity Specification for Air), these specifications set limits for contaminants like carbon monoxide, water vapor, and oil mist produced by your breathing air compressor.
Each grade, such as Grade D, Grade E, or Grade L, defines purity requirements for a specific use case:
These standards have been integrated into both the Occupational Safety and Health Administration (OSHA) and National Fire Protection Association (NFPA) regulations, forming the baseline for safety across industries.
Grade D air is suitable for most above-ground SCBA operations (firefighters, HAZMAT, industrial).
Grade E adds stricter oxygen and hydrocarbon controls, standard for SCUBA and pressurized environments.
Meeting Grade E automatically covers Grade D, but not vice versa.
Required by:
Why: Meets OSHA 1910.134, the legal requirement for workplace breathing air.
Grade E is becoming the gold standard for all onshore and underwater operations because of its heightened requirements.
Required by:
Scientific and government divers, like those with the NOAA and EPA, must use breathing air systems that provide CGA Grade E air for SCUBA cylinder fills. Among the many benefits of Grade E compressed breathing air, the stricter limits on O₂ and VOCs prevent toxic buildup under the pressure experienced by divers during operations.
OSHA’s 29 CFR 1910.134 mandates that employer-supplied respirator air meet CGA Grade D or better. The regulation spells out exact contaminant limits and moisture levels.
While OSHA references the 1989 CGA spec, it allows newer updates if they provide “equal or greater protection.”
The NFPA similarly uses CGA Grades as baselines, but with additional considerations. NFPA 1989 requires:
These NFPA criteria exceed both basic CGA Grade D and Grade E specs.
Breathing air compliance isn’t the same for every organization. While breathing air grades provide the baseline purity standards, regulatory bodies such as OSHA, NFPA, and NOAA often layer on stricter requirements. This creates overlap but not perfect alignment.
Key points organizations need to be aware of:
Bottom line: Departments can’t assume that meeting a CGA grade automatically satisfies OSHA, NFPA, or NOAA. Compliance depends on the regulatory environment you operate in, and often exceeding the base CGA grade is the only way to truly cover all requirements.
Air with 20–22% O₂, ≤10 ppm CO, ≤1,000 ppm CO₂, ≤5 mg/m³ oil, and ≤25 ppm total hydrocarbons. Used for SCUBA and high-pressure breathing air.
Grade E has a tighter O₂ range and requires VOC testing. Grade D is broader and doesn’t check total hydrocarbons.
Firefighter SCBA compressors are required to provide CGA Grade D breathing air, while CGA Grade E is recommended and required for dive operations. Either way, though, firefighters’ breathing air must meet NFPA 1989 standards.
Not always. NFPA 1989 is stricter than CGA Grade E, requiring ≤5 ppm CO (vs 10 ppm) and a dew point 10 °F below the lowest expected temperature. Air that meets Grade E may still fall short of NFPA 1989 unless further conditioned and verified.
NFPA requires quarterly testing of fire department SCBA compressors. OSHA requires ongoing compliance, but doesn’t set a frequency.
Yes, though many dive operations aim for even stricter standards than Grade E (e.g., ≤2 ppm CO, ≤0.5 mg/m³ oil).
Although not required, it is highly recommended. From helping SCBA gear last longer and protect from the most subtle contaminants to future-proofing breathing air operations, the overall benefits of CGA Grade E are what make it the Gold Standard in compressed breathing air.
Every Arctic SCBA compressor is engineered not only to meet CGA Grade D and E, but to surpass NFPA 1989’s added requirements. From real-time CO monitoring to ultra-low dew point filtration and test-ready sampling ports, Arctic systems ensure your department or dive team stays compliant with the highest standards.
That’s why Arctic Compressor systems aren’t just built to a CGA grade – they’re Truly American-Made™ to cover the full spectrum of OSHA, NFPA, and NOAA requirements, ensuring safe breathing air in every mission-critical environment.
