Ohio Rev. Code § 1567.60: Recording pressure gauge.

The operator of any underground mine shall have a U tube or recording pressure gauge for the purpose of recording pressure or vacuum of the main air current installed in such mine. A record of the readings of such gauge shall be kept in a book which shall be accessible to the deputy mine inspector and all of such records of readings shall be kept so accessible for not less than one year.

No operator of a mine shall refuse or neglect to comply with this section.