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Acceptable use of the presence sensing device

Summary A mill operator asked whether a presence-sensing light curtain could serve as a safety control under OSHA’s mill-guarding rule. OSHA said a tested and listed light barrier could replace or support required trip controls if it provided equal or greater protection and was installed, used, and maintained as specified. OSHA would not approve a particular installation in advance.
Document
Federal opinion letter
Agency
Occupational Safety and Health Administration (OSHA)
Document number
1991-04-12
Date issued
April 12, 1991
Status
Active
Status last verified October 9, 2026

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April 12, 1991

Mr. James Kirton
Chief Engineer
[Recipient address omitted]
Dear Mr. Kirton:

Thank you for your inquiry of February 1, concerning the acceptability of the use of a presence sensing device (light curtain) on a mill as the safety controls required by 29 CFR 1910.216(b).

The Occupational Safety and Health Administration (OSHA) will accept protection of employees from hazards when the employer's action provides equal or greater employee protection than an OSHA standard requires. This policy is described in the enclosed section of OSHA Instruction CPL 2.45B, Revised Field Operations Manual.

The ISB light barrier tested and listed by Underwriters Laboratories Inc. (UL) under test outline 491 for fail safe operation may replace or support the safety trip controls on mills or other machinery with machine guarding hazards. The installation and use shall be in accordance with any instruction included in the listing or labelling as required by 29 CFR 1910.303(b)(2). The equipment must also be properly maintained. OSHA cannot give approval in advance of the application of a product, because through improper installation or misuse a hazard may develop.

We appreciate your interest in employee safety and health. If we can be of further assistance, please do not hesitate to contact us.

Enclosure

Sincerely,
Patricia K. Clark, Director
Directorate of Compliance Programs

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