Breathing Air Compressors and Grade D Purification Systems
One team accountable for the OSHA Grade D certificate from compressor intake through the filtration chain and CO monitoring.
What do I need to supply OSHA-compliant breathing air?
OSHA 1910.134 requires Grade D air per CGA G-7.1, which means a breathing air compressor or a purification panel with continuous CO monitoring and the correct filtration chain, sized to the number of respirators you run at once. The compressor intake must sit clear of exhaust and contaminant sources, and the delivered air has to hold 19.5 to 23.5 percent oxygen with CO at or below 10 ppm. We design, install, and test the full chain so one team is accountable for the certificate.
Grade D breathing air specification (CGA G-7.1)
| Parameter | Grade D requirement |
|---|---|
| Oxygen | 19.5 to 23.5 percent |
| Carbon monoxide (CO) | 10 ppm maximum |
| Carbon dioxide (CO2) | 1,000 ppm maximum |
| Oil (condensed) | 5 mg/m3 maximum |
| Odor | No pronounced odor |
The standards to cite in your written respiratory protection program: OSHA 29 CFR 1910.134 for the requirement, CGA G-7.1 for the air quality grades.
What a compliant system includes
- Breathing air compressor, or a Grade D purification panel fed from plant air
- Particulate, coalescing, and activated carbon filtration stages in the right order
- Continuous carbon monoxide monitor with audible alarm
- Intake placement verified clear of exhaust, vents, and process contaminants
- Distribution sized to peak simultaneous respirator demand, 4 to 15 cfm per worker
- Scheduled air quality testing with lab certificates for your program file
Where the air source must itself be oil free, for example when the same system feeds product-contact processes, pair the panel with an oil free compressor.
Where our customers use Grade D air
- Abrasive blasting hoods in fabrication and coating shops
- Spray painting and industrial finishing lines
- Confined space entry in tanks, digesters, and vaults
- Chemical handling and other applications across our served industries, including manufacturing and wastewater treatment
The clean source often pairs with oil free compressors and air dryers and filtration. Installation, service and repair, and compressed air audits are backed by 14 Midwest locations.
- 24/7 emergency response, under 2 hour average
- Factory-trained technicians
- 14 Midwest locations across WI, IL, MN, and MO
- Family owned since 1978, Sullair dealer since 1984
Breathing air compliance questions, answered first
Does OSHA require a dedicated breathing air compressor?
No, OSHA 1910.134 requires that the air delivered to a respirator meets Grade D as defined by CGA G-7.1, and there are two compliant paths: a dedicated breathing air compressor, or a purification panel with CO monitoring that conditions air from your existing plant compressor. The right path depends on your compressor type, intake location, and how many respirators you supply.
Can I feed supplied-air respirators from my regular plant compressor?
Yes, if the air is treated to Grade D before it reaches the worker, which in practice means a breathing air purification panel with particulate, coalescing, and activated carbon stages plus a continuous CO monitor with alarm. OSHA also expects the compressor intake to be placed away from contaminant sources and, for oil-lubricated compressors, a high temperature alarm or CO alarm on the machine itself.
How do I size a breathing air system for my crew?
Count the respirators that run at the same time and multiply by the demand of each: a typical supplied-air respirator draws 4 to 15 cfm depending on the hood or mask, so a three-person blast crew in high-flow hoods can need 45 cfm of Grade D air before you add margin. Size the compressor and purification panel to peak simultaneous use, never the average.
How often does breathing air need to be tested?
Test on a schedule your written respiratory protection program defines, and after any system change; quarterly sampling is the common industry practice for plant-supplied Grade D air, and CO must be monitored continuously in real time, not just sampled. Keep the lab certificates on file, because they are the first thing an OSHA inspector asks for.
Get a Grade D system quote from an engineer
Give us your respirator count and application and an engineer will design the compliant breathing air system and its testing plan. Need help fast? We answer 24/7.
Request a quote or book an air audit
Give us your respirator count and application and an engineer will design a Grade D breathing air compressor or purification system and its testing plan. Request a breathing air compliance review for your site. Urgent? Call 800.825.3222, answered 24/7.
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