Each agency head shall comply with all occupational safety and health standards issued under section 6 of the Act, or with alternate standards issued pursuant to this subpart. In complying with section 6 standards, an agency may, upon prior notification to the Secretary, prescribe and enforce more stringent permissible exposure levels or threshold limit values and may require more frequent monitoring of exposures without recourse to the approval procedures for alternate standards described in 1960.17. In addition, after consultation with employees and safety and health committees and prior notification to the Secretary, an agency may utilize the latest edition of a reference standard if it is more stringent than the section 6 standard. After notification, the Secretary may require the use of the approval procedures for alternate standards for any of the situations described in this paragraph.