By Richard L. Parker, MBA, CHFM, FACHE, FASHE
When the lights go out
It is a familiar scene during a survey: a surveyor asks to review the generator test logs. The administrator proudly presents the binder, explaining that their facility’s emergency power system runs on natural gas rather than diesel. The surveyor nods, flips through the pages, and asks, “Can you show me how you document your monthly testing?” A pause follows. The documentation looks different from what most surveyors expect, and that’s where uncertainty begins.
As more ambulatory surgery centers (ASCs) choose natural gas or battery-based power systems, understanding how to demonstrate compliance has never been more important. While the majority of NFPA 110 requirements were written with diesel systems in mind, NFPA 110 and NFPA 111 establish clear expectations for alternate systems. The key for ASC leaders is to know their system, understand its requirements and maintain the documentation that proves compliance.
Diesel systems: The traditional standard
Diesel-driven emergency power supply systems remain the most common in health care. They are referenced throughout NFPA 110, which defines testing intervals and performance expectations. For most ASCs, diesel systems are classified as Type 10, Class 2, Level 1, meaning that power must be restored within 10 seconds, be capable of supporting a minimum two-hour load, and serve functions critical to life safety.
Monthly testing must run for at least 30 minutes under a load of not less than 30 percent of the generator’s nameplate rating, and any generator cool-down period following the test does not count toward the required 30 minutes under load. If the monthly load tests fail to reach that 30 percent threshold, an annual load bank test is required to meet NFPA intent. Every 36 months, a four-hour load test is required. All results must be logged, showing date, duration, load and any corrective actions taken.
Because diesel systems store their own fuel, surveyors often focus on tank condition, maintenance records and the age of stored fuel. Documentation should also include preventive maintenance, battery checks and transfer switch testing. These details demonstrate not only compliance but also operational readiness.
Natural gas systems: Reliable but often misunderstood
Natural gas-powered generators, referred to in NFPA 110 as spark-ignited generators, operate under the same performance intent as diesel systems but have unique differences. NFPA 110 still applies but testing and documentation expectations vary slightly. Unlike diesel, there is no annual load test requirement. Instead, the monthly and 36-month exercises are conducted using the facility’s connected load; no external load bank is needed.
Because the fuel source is continuous, surveyors may seek verification of the fuel supply’s reliability. Documentation should include local utility data confirming service reliability, plus evidence that the system starts automatically, reaches rated voltage and frequency, and can sustain load during testing.
In surveys, the main issue is usually not performance, it’s documentation. Logs must show consistent testing, start-up verification and that all testing is conducted in accordance with manufacturer recommendations. The level of detail should mirror the example provided in NFPA 110, which includes a list of typical log items such as maintenance schedule, power fail, transfer, crank time, AC voltage, frequency, amperage, oil pressure and restoration to normal. Logs should document these operational observations for each monthly exercise, including transfer and retransfer events, voltage and frequency readings, oil pressure, and temperatures, along with any deficiencies and corrective actions.
Battery systems: Compliance under NFPA 111
Battery-based systems, or stored emergency power supply systems (SEPSS), fall under NFPA 111 rather than NFPA 110. These systems are becoming more common as technology improves and facilities pursue quieter, cleaner and lower-maintenance backup options.
In surgical environments, a Level 1 SEPSS is expected, as a power failure could result in loss of life or serious injury. Level 1 systems must supply power of sufficient quality to ensure safe operation of connected equipment for the duration defined by the system’s class – often 30 minutes to two hours.
NFPA 111 outlines detailed expectations for maintenance, inspection and testing:
- Systems must be maintained to ensure readiness and tested immediately after any repair or battery replacement.
- A reproducible record of all inspections, tests and repairs must be kept on-site, showing logs, corrective actions, service personnel and documentation of completed tests.
- Monthly inspections verify cleanliness, electrolyte levels (where applicable) and the condition of terminals, connections and indicators. Individual cell voltages and pilot cell gravity should be checked and recorded when practical.
- Annual load testing must confirm the system can carry at least 60 percent of its rated class load for its full duration. If ohmic testing is used and results remain within acceptable limits, the annual full-load test can be deferred.
- All maintenance and testing must be performed by qualified personnel, with records accessible to the authority having jurisdiction.
The core message for survey readiness is consistency. Every ASC using a battery-based system should have organized documentation that shows testing intervals, qualified personnel, corrective actions and evidence that the system remains capable of supporting its designated load. Missing records or incomplete logs are the most frequent findings during surveys.
Survey documentation and readiness
Regardless of system type, the surveyor’s focus is the same: proof of reliability. Surveyors will typically ask three questions:
- How do you test the system?
- How do you document the results?
- Who performs the testing?
Facilities should be able to provide a clear answer supported by records. Logs should include testing frequency, load details, and the name of the person performing or overseeing the test. Corrective actions and repairs should be traceable to follow-up verification.
ASC leaders should also ensure that staff can describe what happens during a power failure. Knowing that “the generator starts within 10 seconds” or “the battery backup provides 30 minutes of power” shows operational understanding, not just compliance.
Takeaway for ASC leaders
Energy sources may differ – diesel, natural gas or battery – but the expectation remains the same: the emergency power system must reliably support surgical operations when normal power fails.
Every ASC leader is responsible for understanding their system’s requirements, maintaining complete documentation and demonstrating that it meets the applicable NFPA standards. Compliance is not just about passing a survey, it’s about ensuring patient safety and operational readiness every time the lights flicker.
– Richard L. Parker is associate director, physical environment and life safety at Accreditation Commission for Health Care, Inc. where he provides guidance to customers and surveyors in the ASC and hospital programs.
