Extension cords are off the ground (or to side of walkway) not creating trip hazards at any walkway or pathway. 

Okland

Subpart K (1)(b) pg 35

Electrical cords, welding leads, and cables shall be covered, elevated or otherwise protected from damage and from creating additional hazards to employees (e.g., they must not be run in the middle of hallways, walkways, or stairs nor can they be routed in or under water or ice).

OSHA

1926.405(2)(ii)(I)