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 https://www.osha.gov.

May 15, 1996

Mr. Dan Chisholm
Motor and Generator Institute
Post Office Box 2474
Winter Park, Florida 32790-2474

Dear Mr. Chisholm:

This is in response to your letter of January 29, and your facsimiles regarding electrical generators in hospitals and the Occupational Safety and Health Administration's (OSHA's) Standard, The Control of Hazardous Energy (Lockout/Tagout), 29 CFR 1910.147.

From your letters, we understand that your situation is as follows:

a. Employees have to inspect prime movers (engines) that are part of on-site electrical generators in hospitals, whose purpose is to supply electricity to critical circuits (patient life saving devices) in case of power failure. These machines have to be constantly monitored to assure that they are in excellent mechanical condition and therefore able to withstand the strain and demands placed on them in case of an emergency;

b. The employees that conduct the servicing/inspections must comply with the Lockout/tagout standard, 1910.147;

c. Similarly, however, the National Fire Protection Agency's (NFPA's) and the Joint Commission on Accreditation of Health Care Organization's (JCAHO's) requirements indicate that emergency generators have to be automatically started in case of a power failure, and be able to supply electricity to the building's emergency circuits in 10 seconds or less;

d. If an employer had to comply with [c], above, it would not seem possible to comply with the Lockout/Tagout standard;

e. If an employer does not comply with OSHA's lockout/tagout standard, the employees lives would be at stake. The prime mover on an Emergency Power Supply System is a large diesel engine with 4-16 cylinders. A machine this size requires periodic maintenance and daily observation of several components attached to the engine or generator. For a technician to perform these functions, he must put himself in a position, in relation to the equipment, to possibly be injured if the machine were to start automatically, if the control devices were not locked out to prevent the release of stored energy, for example, injury could occur when fan belts must be inspected for wear, if the belt would start automatically; and

f. Finally, placing the emergency generators in a locked-out position whereby the unit will not be able to come on line within 10 seconds prescribed by the NFPA standards may jeopardize a hospitalized patient's life.

OSHA's standard for the control of hazardous energy sources, 1910.147, requires employers to establish and implement procedures to disable machinery and equipment and to prevent the release of hazardous energy sources while maintenance and servicing activities are being performed. Before any employee performs any servicing or maintenance on a machine or equipment where the unexpected energizing, start up, or release of stored energy could occur or cause injury, the machine or equipment must be isolated and rendered inoperative.

OSHA has not adopted NFPA 99 or NFPA 110; therefore, the Agency does not enforce the requirement in those standards for emergency generators to be capable of supplying electricity to the building's emergency circuits in 10 seconds or less.

OSHA does not regulate public safety functions that are not associated with the health and safety of employees. We do not, however agree that it is an adequate solution to inform personnel in surgical suites or nurses in charge of patients with life support systems of the planned servicing and the possibility of an unexpected power outage. Further, just as the generator would be incapacitated during any repair activity, it should also be isolated and rendered inoperative when employees are performing maintenance activity exposing them to injury due to the unexpected start up of the generator.

We believe that there are measures that employers can take to minimize the impact on patient safety and to meet the intent of the NFPA standards and still meet the OSHA standard. One measure that you did not mention is to provide two backup generators (the one present and an additional one). Such an approach would ensure the safety of both patients and employees. One generator could be hooked up to operate in case of an emergency, while the other one is being serviced in compliance with the Lockout/Tagout standard and vice versa.

We appreciate your interest in occupational safety and health. If you need further assistance, please contact Alcmene Haloftis of my staff at 202-219-8031.


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