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.
Recording pressure gauge
Ohio Rev. Code Ann. § 1567.60, under Chapter 1567 | Mine Equipment; Safety Provisions.
Ohio Rev. Code Ann. § 1567.60