These open the OEM site. Save copies to your device for offline reference once you find what you need.
Kaeser
Search 'service' or contact local rep for manuals
Ingersoll Rand
Customer Care → Manuals & Parts
Atlas Copco
Customer Center → Spare parts & service
Chicago Pneumatic
Service & Parts section
Quincy Compressor
Customer Support → Manuals & Tools
Sullair
Service & Support
Gardner Denver
Contact Customer Service for docs
Campbell Hausfeld
Customer Service → Manuals
Champion Pneumatic
Literature / Resources
FS-Curtis
Literature & parts lookup
Hitachi Industrial
Industrial air compressors
Mattei
Rotary vane resources
ELGi
Service & support
Powerex
Medical & oil-less
Sullivan-Palatek
Manuals via dealer network
BOGE
Service downloads
CompAir
Service & support
Rogers Machinery
Custom-built compressor docs via support
Doosan Portable Power
Portable / tow-behind units
Rolair
Manuals & parts
DeWalt / Emglo
Portable compressors — Service & Support
Missing a brand? Let me know and I'll add it.