I usually avoid these discussions, but we sometimes forget there is another AHJ out there besides the local authorities. From 29CFR:The definitions from 1910.399 are not in actual Section order, but I think they make a bit more sense this way.
Section 1910.303(a) is pretty standard jargon.
I love the 1910.399 definition of Approved - it leaves no doubt who the AHJ is.
Acceptable is the key term. If you read the three subparts carefully, you will see that it essentially says that if something can be ??accepted, or certified, or listed, or labeled, or otherwise determined to be safe by a nationally recognized testing laboratory ?? it must be. Only when ??an installation or equipment of a kind that no nationally recognized testing laboratory accepts, certifies, lists, labels, or determines to be safe?? is alternate (2) or (3) permitted. Even then, alternate (3) is only permitted if (2) doesn?t result in a disapproval.
Very few installations are truly ?OSHA ?free?, even residential. As long as an employer/employee relationship ? no matter how tenuous ? can be attached to an installation, Fed or a State OSHA can technically claim jurisdiction. The fact that they don?t more often is a matter of available resources, not authority.