Emergency lighting insights

• Electrical and life safety engineers must understand NFPA 101: Life Safety Code to ensure emergency lighting systems provide adequate illumination for safe egress during power outages or emergencies.
• The code outlines specific requirements for placement, duration and intensity of emergency lighting to meet life safety standards in various building occupancies.
• This article surveys some of the more popular codes, providing references for key provisions governing emergency lighting installations. Applicability of specific codes will depend on adoption by local jurisdictions.

“Emergency lighting” refers to the systems and equipment that illuminate a building when normal power fails. Its primary purpose is to facilitate quick, safe egress, so it’s overwhelmingly directed at lighting and marking the paths to building exits, particularly to escape a fire or other advancing peril. Other purposes include support of rescue efforts, support of power restoration efforts and amelioration of the tendency of building occupants to panic when suddenly and unexpectedly immersed in darkness.

In view of the importance of emergency lighting to the safety of building occupants, the various building codes and the plan reviewers, building inspectors and fire marshals that enforce them take a serious view of emergency lighting requirements. A thorough understanding of code requirements for emergency lighting is essential to get a set of documents through permit and to get a facility to a certificate of occupancy.

The sometimes-arcane language of the codes might lead to differences of opinion about what their various provisions mean. Where any doubt exists, it’s important to clarify requirements with authorities having jurisdiction (AHJ) ahead of permit and construction to avoid embarrassment and unpleasant surprises at completion.

Emergency lighting codes and standards

Figure 1: A battery-powered light unit in the corridor of a business occupancy. The test switch and indication lamp can be seen adjacent to the luminaire. Courtesy: Johnston, LLC

The codes listed below provide requirements for emergency lighting systems. These editions are referenced in this article:

• International Building Code (IBC), 2021 edition: The IBC sets minimum requirements for building systems. It’s enforced by most jurisdictions in the United States. Requirements for emergency lighting are found in Sections 1008, Means of Egress Illumination and in 1013, Exit Signs.
• NFPA 70: National Electrical Code (NEC), 2023 edition: The NEC is the installation code covering requirements for electrical equipment and installations. The NEC is enforced by an overwhelming majority of jurisdictions in the United States and in many other parts of the world. All emergency lighting is powered from building electrical systems; consequently, many sections of the NEC describe requirements related to emergency lighting systems. The portions of the NEC most directly affecting emergency lighting are found in Article 700, Emergency Systems.
• NFPA 99: Health Care Facilities Code, 2021 edition: NFPA 99 describes requirements for systems installed in health care facilities. Standby lighting that functions much like emergency lighting is required for a few specific locations in NFPA 99.
• NFPA 101: Life Safety Code, 2021 edition: NFPA 101 defines minimum building requirements to provide a measure of protection to building’s occupants from fire, smoke, toxic fumes and other hazards. NFPA 101 is intensely concerned with building egress and therefore with illumination of egress paths under emergency conditions. Emergency lighting requirements are detailed in Sections 7.8, Illumination of Means of Egress; 7.9, Emergency Lighting; and 7.10, Marking of Means of Egress.
• NFPA 110: Standard for Emergency and Standby Power Systems, 2022 edition: NFPA 110 prescribes requirements for emergency power systems — primarily, but not exclusively generators — that support loads whose failure could result in severe injury to humans. A few portions of NFPA 110 are specifically applicable to emergency lighting: Chapter 4, Classification of Emergency Power Supply Systems; 7.3, Lighting at the generator location; and 8.3, Maintenance and Operational Testing
• NFPA 111: Standard on Stored Electrical Energy Emergency and Standby Power Systems, 2022 edition. NFPA 111 primarily covers battery-supported systems, though it also covers fuel-cell systems. It does not cover battery-supported luminaires. Applicable chapters include Chapter 4, Classification of Stored-Energy Emergency Power Supply Systems and Chapter 8, Routine Maintenance and Operational Testing.

Buildings and occupancies that require emergency lighting

The IBC requires emergency lighting for all buildings, with exceptions for Group U: utility buildings; Group R: dwelling units in residential occupancies; and Group I: sleeping units in institutional occupancies. When a building’s primary electrical supply is available, egress lighting must be served from that supply. When the primary supply fails, egress lighting in pathways that lead to exits, and exit discharges must be illuminated by an emergency power supply (IBC 1008. 3). The emergency supply may take the form of an external generator, a central battery system or a distributed set of batteries serving individual luminaires.

Figure 2: A supplementary, motion-sensitive, battery-powered luminaire in the stairwell of an apartment house. This unit is not listed for emergency use. Powered by primary batteries, its purpose is to provide illumination for the residents’ convenience after emergency batteries in bona fide emergency fixtures have discharged. Courtesy: Johnston, LLC

The IBC’s requirements for emergency lighting are restricted to buildings that require two or more exits. Buildings requiring only one exit are defined in Table 1006.2.1 based on their occupancy types, occupant loads, common path of egress travel and whether they are sprinklered.

The requirements of NFPA 101 are similar, though expressed differently. Where the IBC provides a short list of buildings that do not require emergency lighting, NFPA 101 provides a long list of building occupancies in Chapters 11 through 43 and lists emergency lighting requirements for each. No emergency lighting requirements are described for one- and two-family dwellings or for rooming houses (Chapters 24 and 26, respectively). Some form of emergency lighting is required for all other building occupancies, often based on building height or number of occupants.

Both the IBC and NFPA 101 require exit signs, continuously illuminated, in all occupancies. The IBC lists exceptions for utility buildings, residential sleeping rooms and institutional sleeping rooms (1013.1). NFPA 101 lists requirements for exit signs in Chapters 11 through 43, describing exit sign requirements for individual occupancies. All occupancies other than one- and two-family dwellings and rooming houses show requirements for exit signs.

In general, the IBC applies to new buildings and renovated areas. New provisions are not normally enforced retroactively on existing buildings, except where an AHJ determines that existing conditions do not adequately provide for public safety (IBC 102.6). In contrast, NFPA 101 lists requirements for both new and existing buildings and is enforceable on all buildings in jurisdictions where it is adopted.

Where to locate emergency lights

NFPA 101 requires emergency lighting along all designated exit access components of the building including corridors, stairs and other passages that lead to an exit or from an exit discharge to a public way (7.9.1.2). “Designated components” refers to those exit pathways that are valid exit paths as determined by the AHJ. Excluded pathways that may well lead to outside the building are paths that are not legal for public exit including, for example, paths that lead through electrical or mechanical rooms or across ramps that are too steep. Requirements for the location of emergency lighting in the IBC are functionally identical to those of NFPA 101.

Figure 3: Artist’s conception of an exit sign using a pictogram. The pictogram is called “Running Man,” and is commonly used in Europe, where the diversity of language is much greater than in the United States. Under NFPA 101, similar pictograms may appear on exit signs in the United States with authority having jurisdiction approval. Courtesy: Johnston, LLC

The IBC also requires emergency lighting in certain nonegress spaces to enable building personnel and emergency responders to support fire rescue efforts. Those spaces include fire command centers and rooms housing electrical equipment, fire pumps or generators. A requirement for emergency lighting in public restrooms larger than 300 square feet is included to facilitate egress for occupants unfamiliar with the room layout

NFPA 101 and the IBC each require illuminated exit signs at exits and along egress paths, to visibly mark the various egress components in the building (NFPA 101 7.10.1.2; IBC 1013.1). Exit signs along egress paths must be located to ensure that an exit sign is within the lesser of 100 feet of any point along the paths or the listed viewing distance of the sign (NFPA 101 7.10.1.5.2; IBC 1013.1). In practice, all exit signs have a listed viewing distance of 100 feet. Neither code requires exit signs for main exterior doors that are obviously exits.

Both codes also contain provisions for exit signs installed near the floor level. The IBC references these signs for R-1 occupancies, such as hotels, outside sleeping rooms or dwelling units (1013.2). NFPA 101 describes similar signs and references Chapters 11 through 43 for occupancies where such signs are required (7.10.1.7). Low exit signs are currently required in special amusement buildings, a type of assembly occupancy, under NFPA 101, Assembly Occupancies.

NFPA 110 requires battery-powered lighting at generator set locations, other than in outdoor enclosures without walk-in access (7.3). Because the purpose of this lighting is to facilitate work on a failed generator, it cannot be supported by the generator alone. The battery’s charging equipment must be served from the load contact of a transfer switch. A similar, less extensive requirement appears in NFPA 99 (6.7.5.1.2.4(4)).

NFPA 99 requires battery battery-powered lighting where general anesthesia or deep sedation is used (NFPA 99 6.3.2. 6.1). These luminaires are intended to continuously maintain a level of illumination where invasive procedures are performed, so that a surgeon performing a delicate procedure will not suddenly be left in total darkness should normal power fail and to provide minimal level illumination to allow the surgeon to terminate the procedure in the event that standby lighting fail to illuminate. These luminaires do not technically comprise emergency lighting, as facilities covered by NEC Article 517 have essential systems providing standby power and do not strictly have emergency systems.

Performance requirements per code

Typical performance requirements for emergency egress illumination are well-harmonized between NFPA 101 and the IBC. Power must be provided to emergency lighting within 10 seconds after a normal power outage (NFPA 101 7.9.1.3; IBC 2702.1.4). Emergency lighting must persist for 90 minutes after loss of normal power. The initial illumination along the egress path at the floor level must be an average of 1 footcandle (fc) and no less than 0.1 fc at any point.

Figure 4: A battery-powered lighting unit in an exit stairwell. Courtesy: Johnston, LLC

After 1½ hours of continuous operation, Illumination must not decline below an average of 0.6 fc, with a minimum of 0.06 fc. The ratio between the maximum and minimum illumination levels along the path may not exceed 40 to one (NFPA 101 7.9.2; IBC 1008.3.4 & 5).

NFPA 101 specifically calls for new emergency lighting power systems to be at least Type 10, Class 1.5, Level 1 systems, as defined in NFPA 110 (7.9.2.2). NFPA 110 identifies a Level 1 system as one whose failure could result in death or severe injury to humans. System type is defined as the maximum time, in seconds, that the emergency system may be without power. System class is defined as the minimum time that the system will serve rated load without refueling or recharging (4.1).

The NEC requires that storage batteries and uninterruptible power supply systems that support emergency lighting systems maintain their output voltage at 87.5% of nominal for 90 minutes (700.12)

Emergency illumination requirements for stairways are subject to interpretation under NFPA 101. Emergency illumination requirements provide specific levels for the egress path, but do not mention stairways (7.9.2.1.1). Section 7.8, Illumination of Means of Egress, requires that stairs be illuminated at 10 fc “during conditions of stair use.” Requirements in 7.8 are higher than those covering emergency lighting in 7.9, suggesting — but not directly stating — that illumination levels described in 7.8 cover requirements for lighting under normal power conditions.

AHJs have attempted to enforce the 10-fc rule on emergency lighting in stairways. Where generators provide emergency power, compliance with such a rule is not difficult because emergency lights operate at full illumination on generator power. Battery-powered lighting units, on the other hand, operate at a fraction of their normal lighting level on emergency power, making compliance with a 10 fc rule difficult or unreasonable.

The IBC and NFPA 101 say little about performance requirements for exit signs, except to note that they must remain adequately illuminated to be seen from their listed viewing distances for at least 90 minutes after normal power fails. The two codes instead focus on physical characteristics of the signs and their listings. The IBC permits only the legend, “EXIT,” on exit signs (1013.6.1). NFPA 101 requires that same legend, but permits “other appropriate wording,” and allows for use of pictograms from NFPA 170: Standard for Fire Safety and Emergency Symbols with AHJ approval (7.10.3).

Testing and maintenance requirements

Testing requirements for emergency lighting are found in NFPA 101. Testing may be performed manually or by an automatic system. Written records of testing are required, generated manually or automatically, depending on the test method employed (7.9.3.1). Functional testing is required monthly for at least 30 seconds with the equipment under test fully functional.

For manual tests of battery-powered lighting units, an operator will press a button at or near the luminaire that disconnects the luminaire from normal power and connects it to its battery for as long as the button is depressed. Longer functional tests are required annually, for a period of 90 minutes. For these tests, lighting circuits are typically de-energized and personnel observe adequate function throughout the test area.

Figure 5: Unit equipment in the corridor of a residential occupancy. This unit is normally not illuminated and automatically comes on when normal power fails. Courtesy: Johnston, LLC

For generator-based systems and stored battery systems, NFPA 101 states that testing “shall be permitted to be conducted in accordance with 7.9.2.4” (7.9.3.1.4). The referenced section states that generators and appurtenances serving emergency lighting shall be installed and maintained in accordance with NFPA 110 and stored energy systems in accordance with NFPA 111.

Testing and maintaining those systems as described in their respective codes would meet the testing requirements of NFPA 101 for emergency lighting systems, whether illumination levels were tested or observed. It’s not entirely unlikely, though, that an AHJ would require that emergency luminaires themselves be assessed connected to the emergency power system and their proper function observed and recorded.

NFPA 110 and NFPA 111 each describe requirements for initial acceptance testing (NFPA 110 7.13; NFPA 111 7.6) and for routine maintenance and operational testing (NFPA 110 8; NFPA 111 8). A detailed description of testing requirements is too lengthy to present here. Acceptance testing requirements are highly prescriptive, requiring several inspections, at least two rounds of load testing and logging of system performance and conditions.

In broad terms, maintenance testing requirements for generator systems call for monthly load testing with 30% load, with the exhaust at the manufacturer’s recommended operating temperature and with additional testing where those parameters can’t be achieved (NFPA 110 8.4.2.1). NFPA 111 does not directly prescribe load testing procedures for storage battery systems, deferring to the system manufacturer’s recommendations (8.4.1).

Does the electrical system include emergency lighting?

The installation requirements for power systems serving emergency loads, including emergency lighting, appear in NEC Article 700, Emergency Systems. These requirements cover all the loads of the emergency power system, including emergency lighting. This section focuses on those requirements that most directly affect emergency lighting.

Note that health care facilities technically don’t have an emergency system; however, their life safety branch falls under Article 700, except where amended in Article 517 or in NFPA 99 (NEC 517.26; NFPA 99 6.7.6.2.1.5).

Article 700 requires that emergency system wiring be entirely independent of all other wiring (700.10(B)), with limited exceptions. Those exceptions are necessary to implement the intended transfer operations of the system or to bring the wiring to a point in the standby system where the emergency system originates. Emergency wiring and other wiring may enter the same enclosures of transfer switches and similar equipment that selects between available sources (700.10(B)(1)-(4)) and it may originate in the same distribution equipment as other circuits provided that a degree of separation is maintained. Emergency lighting and power circuits may serve none but required emergency loads (700.15).

The emergency system capacity must be adequate to serve all the loads connected to the system simultaneously, as calculated by one of the methods described in Parts I through IV of Article 220: Branch-Circuit, Feeder and Service Load Calculations. The system may serve nonemergency loads as well, if it has “adequate capacity,” or a load shed system to selectively shed other loads in favor of the emergency system (700.4(B)).

Essential systems for health care facilities are not required to be sized for Article 220 load calculations. Instead, those systems must have adequate capacity to meet the actual demand presented by their connected loads (NEC 517.31(D); NFPA 99 6.7.1.2.4).

Overcurrent protection devices on the emergency power system must be selectively coordinated with all upstream devices. The definition of “selective coordination” in the NEC is quite strict, requiring coordination for the “full range” of overcurrent settings and device operating times. In a typical standby generator system serving optional load along with emergency load, the optional load will be many times larger than the total load of the emergency system, making selective coordination difficult.

For single generator systems, it is permissible to install a separate circuit breaker to serve emergency system at the generator terminals, obviating concerns about upstream coordination. In health care facilities, selective coordination is required only for faults that persist longer than 0.1 seconds (NEC 517.31(G); NFPA 99 6.7.2.1.1).

Emergency system feeders and generator control circuits must be protected from fire by one of several methods in large assembly occupancies, large educational occupancies and high-rise buildings (700.10(D)). For health care occupancies, this requirement does not apply (NEC 517.26(2); NFPA 99 6.7.6.2.1.5(B)(2)). Feeder-circuit equipment must be in rooms with either a two-hour fire rating or fire sprinkler protection.

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