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NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.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

May 1, 1990

Mr. Chuck Mullen, Jr. Corporate Safety Coordinator Precision Twist Drill Company 301 Industrial Avenue Crystal Lake, Illinois 60014

Dear Mr. Mullen:

Thank you for your letter of February 21, addressed to Secretary of Labor Elizabeth Dole, concerning the new lockout/tagout standard, 29 CFR 1910.147. Please excuse the delay in our response.

Normal production operations, such as tool changes, cleaning, unjamming, servicing and making adjustments to machines, which are routine, repetitive and integral to the use of the equipment for production are not covered by the requirements of 29 CFR 1910.147, if the work is performed using alternative protective measures which ensure employee safety. Lockout or tagout is not required by this standard if the employer can demonstrate that the alternative means enable employees to service the machine without being exposed to unexpected activation of the equipment or release of stored energy. Production safeguards conforming to the requirements of 29 CFR 1910, Subpart O, and the applicable American National Standards Institute (ANSI) standard which provide for control of, or safeguarding from, hazardous energy release(s) and which are not bypassed or rendered ineffective are acceptable alternative means of protection. Typical ANSI standards which contain such provisions are listed in the enclosure, which is not all inclusive.

29 CFR 1910.147 specifically addresses practices and procedures that are necessary to disable machinery or equipment to prevent the release of potentially hazardous energy while maintenance and servicing activities are being performed by employees. Servicing and maintenance functions, normally conducted by the machine or process equipment operator and for which safeguarding provisions in compliance with Subpart O ensure hazardous energy control, are regulated by 29 CFR 1910.147 whenever the normal machine safeguarding is ineffective or rendered ineffective.

It is not apparent, from the information provided with your letter, that your normal operator machine safety guards and/or devices provide for protection of set-up persons from the inadvertent energization of machine components. If the normal operator safety guards and/or devices assure employee protection from unexpected machine component energization during set-up procedures, the standard at 29 CFR 1910.147 would not be applicable. However, if such protection is not assured and it is your intent to provide for compliance with the lockout/tagout standard through implementation of the enclosed set-up procedure, our review identified serious deficiencies. In order to provide further guidance regarding your obligations under the new lockout/tagout standard we offer the following information.

The standard at 29 CFR 1910.147(c)(4) requires that procedures be developed, documented and utilized for the control of potentially hazardous energy. The procedures must clearly outline the scope, purpose, authorization, rules and techniques to be used. The procedures must identify each specific equipment and it's unique energy isolation requirements. (Generic procedures are permitted for similar equipment.) Energy isolation devices must be identified as well as the procedures for shut-down, lockout/tagout and deenergization verification. Operators who are required and/or permitted to engage in maintenance/servicing functions requiring lockout/tagout are designated as "authorized employees" and must receive comprehensive training regarding the mandatory procedures for lockout/tagout as required at 29 CFR 1910.147(c)(7).

Prior to beginning maintenance/servicing operations, the equipment must be deenergized and locked-out or tagged-out as required at 29 CFR 1910.147(c)(5), (c)(7), and (d). All potentially hazardous energy sources must be deenergized, therefore all pressurized air supplies (air lines), or other energy sources, must also be controlled.

In the event that a tagout procedure is to be used, the standard requires more extensive procedures than those required if lockout is used. Please refer to 29 CFR 1910.147(c)(2),(c)(3),(c)(5), and (d)(4).

A copy of the standard is enclosed. If we may be of further assistance please contact us.


Gerard F. Scannell Assistant Secretary