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Ambulatory Surgical Centers and Emergency Power

Ambulatory Surgical Centers and Emergency Power

There has been considerable debate in recent years as to the emergency electrical power needs of freestanding, outpatient ambulatory surgical centers (ASCs).

There has been considerable debate in recent years as to the emergency electrical power needs of freestanding, outpatient ambulatory surgical centers (ASCs). This may seem odd when you consider that emergency power requirements for health-care facilities have been codified since the early 1960s via a National Fire Protection Association (NFPA) standard on the subject. Originally a standard just for hospitals (designated NFPA 76A, Standard for Essential Electrical Systems for Hospitals), the document's scope was expanded to all health-care facilities in 1971, thus making it applicable to ASCs. In 1984, this document was incorporated along with 13 other health-care documents developed by the NFPA Technical Committee on Health Care Facilities into what is now NFPA 99, Standard for Health Care Facilities.

The main issues surrounding this subject are what system is adequate to meet the needs of an ASC, and how long should such a system be capable of providing (or required to provide) power in the event of loss of normal power? Although a few simple answers could be provided, it was observed at a recent conference in California (organized by the authors of this article) that the needs of ASCs are not identical — nor is one emergency power supply system configuration of the essential electrical system practical or possible for all ASCs.

What issues should be addressed during the design and installation period when the type and capabilities of the essential electrical system are being specified? This situation involves more than just the equipment that will be supplying electrical power when normal power is interrupted. The extent of power, the quality of the power, and location of the power source are just a few of the many issues that need to be reviewed. Let's address seven key questions that arise on these types of projects.

  1. How many transfer switches (minimum) are necessary for ASCs?

    The answer is simple: It depends. If the load on the essential electrical system is less than 150kVA, NFPA 99 states that a facility can install just one transfer switch. However, all other requirements for essential electrical systems must be followed. It also needs to be noted that, with only one transfer switch for transferring power from the normal source to emergency power source, its failure essentially shuts down the delivery of power from the emergency power supply. Even if the essential electrical load is less than 150kVA, an ASC can install more than one transfer switch.

    If the essential electrical load is more than 150kVA, an ASC with critical patient care areas, or those using electrical life-support equipment, would have to follow the requirements for a Type 1 EES, as listed in NFPA 99, Chapter 4. This could become complicated for those ASCs located within a commercial building.

    Unlike a hospital (with no independent tenants), the wiring of the ASC portion would have to meet more stringent requirements, including the installation and coordination of ground-fault interrupters (GFIs). The number of transfer switches would increase, because NFPA 99 requires a transfer switch for each branch of the emergency system and a transfer switch for the equipment system, which could entail three transfer switches (one for non-delayed items, delayed-automatic items, and delayed automatic or manual items). All of these possibilities must be reviewed before determining how many transfer switches (at minimum) will be required.

  2. Is a short (10-second) interruption of normal power always acceptable?

    In 1960, a time of 10 seconds (maximum) was established with respect to how long an alternate power system could take to come online and replace the normal power source (i.e., once it was determined that the normal power supply coming into a facility or suite had been interrupted — as opposed to a momentary interruption or dip).

    In the '60s, the mechanics of starting an engine, then connecting it to a generator and the power becoming relatively stable, took about 7 to 8 seconds. The technical members of the committee developing the standard for essential electrical systems wanted a safety factor included (e.g., in case the engine didn't start the first time), so they requested a 10-second criteria. At that time, the medical members of the Technical Committee could accept this scenario.

    This time interval (from recognizing loss of normal power to transfer to emergency power source, using engine-generator systems that require some time before being able to supply electrical power) has not been changed since then. Today, however, there are electrical devices (e.g., computers, digital monitors) that cannot tolerate even 1/60th of a second interruption of power without shutting down or operating incorrectly. Some of these electrical devices are medical devices that either provide life-support functions to patients connected to them or produce extremely vital, real-time information to doctors while treating patients. As such, other methods to maintain a constant supply of electricity have become necessary.

    One method is the inclusion of a battery within a device that allows the device to continue operating normally for some (short) period of time when regular power is interrupted. Another is the placement of an uninterruptible power supply (UPS) between the device and normal power circuitry. These methods are not an “emergency power source of the essential electrical system” as discussed in this article; however, they do provide for continuous power (on a limited time basis) to devices until power from the alternate power source is connected to the distribution system of the essential electrical system.

    Variations of the above designs have been developed with the intent of having certain devices powered continuously when normal power is interrupted.

  3. Do I have to use an engine gen-set, or can I use another type of power source?

    There are now quite a few ways to generate AC electricity — from engines connected to generators (the traditional way) to batteries connected to DC-to-AC converters to gas turbines connected to generators — just to name a few. There are also a variety of engine types (diesel, spark-ignited, and flywheel, among others).

    For health-care facility emergency power purposes, the main performance criteria for whatever method used has been the necessity of supplying 60-Hz (AC) power to the electrical loads on the essential electrical system within 10 seconds, and supplying this power for some period of time without requiring a new supply of fuel. Because emergency power became necessary in the later '50s, the most common method used has been the engine-generator configuration. Whatever method is used, it has to meet the 10-second (max) criteria of restoration of power.

  4. Where can alternate power sources be located?

    When requirements for essential electrical systems were first developed, the model used was normal power being supplied by an electric utility company power station through electric wires to the facility. The alternate power source model was an engine-generator system installed on the property of the health-care facility (if a big system was necessary, such as for a hospital). Later, it was permitted to have an engine-generator system (located on the facility's property) supply normal power and have the local utility company be the alternate power source (very few health-care facilities use this method). If an engine-generator system onsite is used for normal power, but the utility company is not reliable enough as an alternate source, then a second engine-generator system must be installed on the premises.

    However, the Technical Committee responsible for essential electrical system requirements was very clear in requiring at least one source of electric power to be located on the property of the health-care facility. This requirement was an assurance that some power would be available if external power for the facility was interrupted. Furthermore, the location of the emergency power source on the property of the ASC, or within a building where the ASC offices are located, was situated so it is protected from rain, snow, floods, winds, vandalism, etc., if located outdoors. If located within a building, then it must also be protected from flooding, sewer backup, a fire within the building, vandalism, etc.

    NFPA 99 originally listed criteria for protecting emergency power sources. Now, NFPA 110 has the main responsibility for all emergency power sources. (NFPA 99 can add additional requirements specifically related to health-care facilities.) One of the major safety measures for an emergency power source located within a building is that it must be enclosed in a room having a 2-hour fire rating.

  5. How long does the emergency power source have to provide power in an ASC?

    The length of time an emergency power source has to be able to provide power without being refueled has generally remained the responsibility of governmental authorities, but other groups and organizations have an influence on the minimum time. Factors used in determining this time include the level of medical/surgical care provided and the probability of natural disasters that can be expected in the area (e.g., hurricane, tornadoes, earthquake).

    If Joint Commission on the Accreditation of Healthcare Organization (JCAHO) accreditation is mandated by a state, or patients are insured through the Center for Medicare & Medicaid Services (CMS), the minimum time required by these two entities need to be obtained.

    For ASCs that do not use electrical life-support equipment or do not have patient care areas meeting the definition of “critical care area,” NFPA 99, Chapter 14 states that a Type 3 essential electrical system can be installed. Requirements for a Type 3 essential electrical system (as listed in Chapter 4, section 4.6 of NFPA 99) require power sufficient for life safety and for the “safe cessation of procedures in progress.” The length of time will vary, depending on the procedures being performed at the ASC, and needs to be determined by staff, including medical, surgical, and nursing personnel.

    For ASCs that do use “electrical life-support equipment,” or have “critical care area(s),” NFPA 99, Chapter 14 states that a Type 1 essential electrical system is to be installed. However, Type 1 system requirements do not specify a minimum number of hours that the essential electrical system has to be able to supply power without having to be refueled or recharged.

    With respect to life safety criteria and minimum operating times of emergency power to safely exit any building, NFPA 101 requires power for emergency lighting, fire alarm systems, etc., to be able to function for a minimum of 1½ hours upon loss of normal electrical power.

    A May 4, 2007, CMS letter to State Agency Directors listed various conditions under which a battery system could be used as the alternate power supply of the EES. While no specific minimum run time (without refueling) was listed, some consultants recommend 4 hours. Each ASC needs to learn what minimum operating time it must meet in order to satisfy all regulatory authorities and non-governmental organizations.

  6. Is the quality of emergency power a factor?

    The power produced by emergency power sources in ASCs has to meet most of the same quality criteria as the main power source, because there will be patients who will be at the same risk as those in hospitals — namely, if inhalation anesthesia is administered, there will be a patient(s) on electrical life-support equipment.

    Similar concerns involve voltage regulation and governors to handle large load variations, particularly as a result of equipment that cycles on and off (e.g., compressors, chillers). Other concerns are those resulting from spikes and harmonics on the power line, and those associated with the proper grounding between the normal and emergency power system.

    For ASCs located in commercial buildings, it may also be necessary to protect critical equipment from abnormal power variations with appropriate power quality equipment. This could be necessary during normal power operation and emergency power operation.

    Although manufacturers are required to indicate on the nameplate the maximum load that its generator system can handle, designers and/or users need to discuss what types of loads will be connected to the emergency power supply system before making a decision on the power supply. While NFPA 99 requires testing the generator system with all expected loads connected, additional tests (dropping the largest loads and then reconnecting them simultaneously) might be useful to learn if the generator system can handle the sudden load.

  7. Are battery-operated lighting units required in operating rooms?

    A requirement for battery-operated lighting units was proposed and accepted for the 1996 edition of NFPA 99. It was the result of concern raised by anesthesiologists on the NFPA 99 T/C on Electrical Systems (and on behalf of all persons working in the operating room during a procedure) regarding the 10-second blackout that would occur when normal power was interrupted. The loss of power even for 10 seconds was becoming intolerable, considering the hazards it exposed many patients to, according to the anesthesiologists. Anesthesiologists argued that having at least some lighting turn on automatically would greatly help them and others working in the operating room tend to the basic needs of patients, prevent tripping over cords, avoid knocking equipment over, and maintain the sterile zone. It would also eliminate the need for anesthesiologists or others to find a flashlight in the dark, and then hold it while tending to patients.

It should be noted, however, that battery-operated emergency lighting units are not part of the normal electrical distribution system, nor are they part of the essential electrical distribution system or “life-safety” measures. They are an interim operational mechanism for supplying some measure of lighting in an operating room when power to general lighting is interrupted for any reason. This interruption does not include the deliberate switching of a wall switch (for general lighting) from on to off in the operating room. These lighting units do have to be installed in accordance with NFPA 70, because they need to be connected to the circuits of general lighting in order to monitor them for power.

The wording added into the 1996 edition of NFPA 99 has been revised over the years. The 2009 edition will make some further modifications with regard to a minimum lighting level, and add testing criteria for the lighting units.

Klein is the president of Burton Klein Associates in Newton, Mass. He can be reached at [email protected]. Ginsburg is general manager of task force solutions in Anaheim, Calif. He can be reached at [email protected].

Sidebar: Additional ASC Resources

Following is a list of some of the applicable documents used by governmental authorities and non-governmental organizations for the installation and maintenance of ambulatory surgical center (ASC) emergency power sources:


  • NFPA 70, National Electrical Code (particularly Art. 517, Health Care Facilities)

  • NFPA 99, Standard for Health Care Facilities (particularly Chapter 4, Electrical Systems, and Chapter 14, Other Health Care Facilities)

  • NFPA 101, Life Safety Code (particularly Chapter 20, New Ambulatory Healthcare Occupancies, and Chapter 21, Existing Ambulatory Healthcare Occupancies)

  • NFPA 110, Stand on Emergency & Standby Power Systems (particularly safety requirements for generator systems)

  • NFPA 111, Standard on Stored Energy Emergency & Standby Power Systems (particularly safety requirements for stored energy power supply systems)


  • Guidelines for Design & Construction of Health Care Facilities (particularly Part 3 - Ambulatory Care Facilities)


  • The Center for Medicare & Medicaid Services (CMS) monitors the care given to patients who are receiving Social Security benefits. Congress requires CMS to use NFPA 101 as the reference document on matters relating to life safety. CMS can inspect hospitals, ASCs, etc., that accept payment by CMS for patient services, or it may have the Joint Commission on the Accreditation of Healthcare Organizations (JCAHO), Accreditation Association of Ambulatory Health Care (AAAHC), or American Association for Accreditation of Ambulatory Surgical Facilities (AAAASF) do the inspection for them.


  • States can have one or more departments inspecting ASCs, such as a Department of Health & Safety (or equivalent) or the State Fire Marshal Office.


  • Local inspectors of emergency power systems for ASCs generally are the city or town's electrical inspectors. They rely on the state in which the city or town is located for the electrical code they will use to approve electrical installations, such as emergency power supplies. Although a few cities still have their own electrical codes, most states use NFPA 70, National Electrical Code, as the basis for electrical installation requirements in their state.


  • JCAHO Environment of Care Standards (for ambulatory care facilities)

  • AAAHC Standards Handbook (beginning with Physical Environment Checklist)

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