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NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.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

August 11, 1994

[Name Withheld]

Dear [Name Withheld]:

Thank you for your inquiry of April 29, concerning the usage of "sensor lights," otherwise known as presence sensing devices (PSD). Related questions, and our responses are as follows:

Question 1:

Have PSD's been approved by the Occupational Safety and Health Administration (OSHA) as machine guarding for punch press machinery?


Yes and no. Although OSHA has a standard that would allow the use of such devices, no third party has taken on the responsibility for the necessary approval called for by that standard.

The enclosed standard (29 CFR 1910.217(c)(3)) allows "point of operation devices," such as PSD's to be used if they protect the operator by:


a. Preventing and/or stopping normal stroking of the press before the operator's hands are inadvertently placed in the point of operation.

b. Preventing the operator from inadvertently reaching into the point of operation, or withdrawing his/her hands if they are inadvertently located in the point of operation, as the dies close,

c. Preventing the operator from inadvertently reaching into the point of operation at all times.

OSHA does not approve or disapprove specific products. However, OSHA requires that all electrical products used by employees must be treated and approved for their intended use by an OSHA Approved Nationally Recognized Testing Laboratory (NRTL). Underwriters Laboratories Inc. (UL) is the only NRTL which is working on the usage of PSD's as safety guards for operational punch presses. To the best of our knowledge, UL has not yet developed a test for this purpose. The address and telephone number of UL are in the enclosed NRTL list.

Question 2:

If PSD's have not been approved as machine guarding for machine power presses by OSHA, why are they being used in American factories?


The OSHA electrical standard (copy enclosed) 29 CFR 1910.303(a) requires electrical parts to be acceptable only if approved. OSHA approved NRTL's test for safety and list or label or otherwise certify electrical parts such as PSD's used as machine guards. Employers utilizing electrical equipment not so tested, listed, labelled or otherwise certified would be in violation of 1910.303(a) and may be cited.

Information associated with listed, labelled, or certified electrical equipment and conductors may be obtained from the NRTL involved. The contact person for UL is:


John Kobacik
Telephone: (708) 272-8800 ext. 42972

We appreciate your interest in employee safety and health. If we can be of further assistance, please contact David Garcia on 202-219-803l xl2l.


John Miles, Jr., Director
Directorate of Compliance Programs


April 29, 1994

[Name Withheld]

To Whom It May Concern:

I have written this letter for information regarding the usage of Sensor Lights. For the purpose of an occupational safety device during the process of operating a Punch Press. Being that I earn my living operating a Punch Press on a daily bases. The information I am seeking affects me personally.

First of all I would like to know if Sensor Lights have been approved by the Federal Occupational Safety and Health Administration. As a means of a safety guard for Punch Press Machinery. If not why are they allowed for usage for that purpose in United States Factories? Second I would like to receive a copy of the Rules, Regulations & Safety Measures pertaining to the usage of Sensor Lights as safety guards in the operational process of Punch Press Machinery.

Thank You