CPC Main Group
E21F 1/00 Ventilation of mines or tunnels; Distribution of ventilating currents (ventilating rooms or spaces in general F24F)
9 direct subcodes
Child Classifications
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- E21F 1/02 Test models (analogue computers therefor G06G7/50)
- E21F 1/04 Air ducts (suspension devices E21F17/02)
- E21F 1/08 Ventilation arrangements in connection with air ducts, e.g. arrangements for mounting ventilators (; ventilators in general F04D)
- E21F 1/10 Air doors (; doors in general E06B)
- E21F 1/14 Air partitions; Air locks (; dams E21F17/103; air locks for foundations E02D)
- E21F 1/16 Shaft covers
- E21F 1/18 Gravity flow ventilation (E21F1/02 - E21F1/16 take precedence)
Top Applicants
Top 10 applicants by patent filingsfor class E21, 2013–2023, worldwide · Source: EPO PATSTAT
- HALLIBURTON ENERGY SERVICES GROUP US 27,652
- SAUDI ARABIAN OIL COMPANY SA 7,755
- PETROCHINA COMPANY 7,025
- BAKER HUGHES US 6,589
- SCHLUMBERGER TECHNOLOGY US 6,151
- SINOPEC (CHINA PETROCHEMICAL CORPORATION) 4,443
- SCHLUMBERGER TECHNOLOGY NL 4,255
- CNPC (CHINA NATIONAL PETROLEUM CORPORATION) 3,991
- SERVICES PETROLIERS SCHLUMBERGER FR 3,300
- SCHLUMBERGER CANADA CA 3,086