Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at

September 27, 1995

Mr. Todd Hamilton
Association Risk Management Consultant
Federated Insurance
121 East Park Square
P.O. Box 328
Owatonna, MN 55060

Dear Mr. Hamilton:

This is in response to your letter of January 5, 1994 which contained questions concerning the Lockout/Tagout Standard, 29 CFR 1910.147. We apologize for the delay in responding to your letter. The questions and answers are as follows:

Q1. Does the Lockout/Tagout Standard, 29 CFR 1910.147, apply to the mechanic who is performing engine maintenance on a combine, tractor or backhoe, etc.?

R. Yes, but only if there is a potential for employee injury as a result of unexpected energization, start-up or release of stored energy during servicing and maintenance of motor vehicles. Whether servicing and maintenance on other components of such vehicles is covered by the Standard, however, is dependent upon what is involved in the servicing and maintenance procedures. If the servicing or maintenance involves the positioning of components such as buckets, blades and machine body parts, the Standard does not apply; if it is done by a construction company. The fact that certain components of these types of vehicles are not covered by the Lockout/Tagout Standard does not mean that appropriate steps do not have to be taken to protect employees engaged in maintenance or servicing of that equipment. Employers should implement whatever steps are necessary to protect employees engaged in such activities.

For purposes of this letter, the term "unexpected energization" will encompass the terms unexpected start-up or release of stored energy.

The requirements of the Lockout/Tagout Standard, 1910.147, apply to all servicing and maintenance operations which take place in "general industry" workplaces, if there are potential hazards related to the unexpected energization of machinery or equipment. The broad scope of coverage of the Lockout/Tagout Standard is confirmed in the March 30, 1993 Federal Register, which contains a supplemental statement of reasons related to the Lockout/Tagout Standard. On page 16620, column 1, of the March 30, 1993 Federal Register, the following statement is made:

"The Lockout/Tagout Standard applies to all "general industry" workplaces, in which hazards associated with the unexpected energization of any machinery and equipment during servicing or maintenance occur."

There is no specific reference in the Lockout/Tagout Standard to servicing and maintenance of motor vehicles, or any other specific type of machinery Or equipment. This is because OSHA expressed the Lockout/Tagout Standard's coverage in performance terms, rather than in industry specific terms. In the preamble of the Lockout/Tagout Standard, however, motor vehicles are discussed and the discussion on page 36657, column 1, is the basis for OSHA's position relative to the type of motor vehicles covered by the Lockout/Tagout Standard. The context of the discussion is whether the Lockout/Tagout Standard should apply to Construction. The pertinent portion of the discussion reads as follows:

"Of additional concern in the imposition of regulations in the construction industry is the uniqueness of the earthmoving equipment, such as lattice boom mobile cranes, front-end loaders, bulldozers, scrappers, and dump trucks. As opposed to maintenance on automobiles, buses and over-the-road trucks where the removal of the ignition key usually ensures that the engine cannot be started and the vehicle may be worked upon, some of the maintenance of the above mentioned earthmoving equipment involves the positioning of components, such as buckets, blades, and machine body parts which present extraordinary hazards and the means to minimize the potential for injury to employees involve additional considerations which were not adequately addressed during the course of the rulemaking proceeding."

Motor vehicles are also briefly discussed one additional time on page 36650, column 3, of the September 1, 1989 Federal Register. The context in which motor vehicles are mentioned is in a table (Table VIII) which is one of the three tables which present tabulations of the results of an OSHA analysis of 83 fatality investigations related to lockout/tagout problems. Table VIII indicates that vehicles were involved in three fatalities resulting from lockout/tagout hazards.

It should be noted that paragraph (d)(2) of 29 CFR 1910.147, per the guidance on page 36646, column 1, of the September 1, 1989 Federal Register, requires that equipment and machinery be shut down or turned off during the performance of servicing or maintenance. Whenever possible, diagnostic procedures should be conducted when equipment is locked out or tagged out. In those cases where that is not possible, alternative steps, per the requirements of Subparts O and M of the 29 CFR 1910 Standards, must be taken to protect employees from harm during such procedures. Employees must be protected to the extent feasible during such diagnostic procedures. Employees should be trained regarding appropriate methods of performing diagnostic procedures. Guards may only be removed, if it is necessary to do so, in order to perform the diagnostic procedures, and then only to the extent which is absolutely necessary. The guards must be replaced as soon as possible. Personal protective equipment must be utilized as needed. As soon as the diagnostic procedures are completed, the equipment and machinery must be locked out or tagged out before any servicing or maintenance is performed.

Paragraph (f)(1) of 29 CFR 1910.147 must be followed when adjustments are made. Adjustments, unless absolutely necessary, must be made while equipment is deenergized. The precautions set forth in the preceding paragraph for diagnostic procedures must be followed when making adjustments which can only be done when equipment or machinery is operating. An example of an adjustment to a motor vehicle which must be done with the engine running is adjustment of the timing.

Q2. Does the automobile mechanic have to have a lockout/tagout when performing routine maintenance such as an oil change or tune up?

R. Yes, but only if there is a potential for employee injury as a result of unexpected energization during servicing or maintenance operations of motor vehicles. All facets of maintenance and servicing activities including diagnostic and adjustment procedures must be addressed in the energy control plan.

Additional guidance is provided relative to the broad scope of the Lockout/Tagout Standard. On page 16621, column 1, of the March 30, 1993 Federal Register, there is a discussion regarding the lack of limitations on the type of equipment and machinery covered by the Lockout/Tagout Standard. The pertinent portion of the discussion is as follows:

"For similar reasons OSHA decided not to limit the standard to particular equipment. By its terms the standard applies only when the unexpected energization or release of stored energy could cause injury to employees. Machines or equipment that present no hazard are excluded from coverage."

Q3. If the Lockout/Tagout Standard is applicable to motor vehicles, will removal of the ignition key switch and disconnection of the battery cable meet the requirements of the standard?

R. Except in those situations where there is a potential for injury from stored energy removal, the ignition key and disconnection of the battery cable should eliminate the potential for unexpected energization during servicing and maintenance activities.

We appreciate your interest in occupational safety and health. If you have any questions regarding the preceding, please contact Alcmene Haloftis of my staff at 202-219-8031.


John B. Miles, Jr., Director
Directorate of Compliance Programs