It is important to understand the changing risk landscape in parking garages that influences fire protection engineers to properly apply new fire protection code requirements.
- Identify the automotive and parking technologies that are changing the risk landscape in parking garages and understand the fire protection challenges these technologies present.
- Understand the impact of electric vehicle (EV) technology and hybrid electric vehicle (HEV) technology on fire risk in garages.
- Identify new code requirements related to parking garage fire protection because of the changing hazard landscape associated with both automotive and parking building technology.
Fire protection insights
- Fire protection challenges in parking garages are evolving due to the increasing presence of electric and hybrid vehicles, which introduce risks such as thermal runaway and higher heat release rates during fires.
- In response, updated fire protection codes like NFPA 88A and NFPA 13 now mandate enhanced sprinkler requirements to mitigate these hazards, although existing open garages may not yet be retrofitted.
According to the U.S. Fire Administration, approximately 650 parking garage fires occur every year in the United States — and these fires can be catastrophic. Estimates from 2024 indicate that the property damage and losses associated with parking garage fires total approximately $8 million. In addition, parking garage fires cause an estimated 15 personal injuries every year.
Hence, fire protection and safety regulations that accurately capture inherent risks are critical in parking garage designs to ensure fire and life safety.
Fire and building codes are largely reactive, which means that code changes are typically implemented in response to changing conditions and technologies that shift the hazard landscape. Over the past several years, new code changes have been enacted in various areas of fire protection as code bodies struggle to advance protection requirements to accommodate new vehicle technologies including increased use of lithium-ion batteries. The hazard landscape of parking garage fire protection has changed drastically over time.
Fire protection hazards are changing
At present, the most obvious change to the hazard landscape for parking garage protection is in response to battery electric vehicle and hybrid electric vehicle (HEV) technologies and relates primarily to battery chemistry including lithium-ion batteries. Lithium-ion battery fires are especially aggressive in these types of vehicles because the heat from a malfunctioning lithium-ion battery cell can cause adjacent cells to fail. Consequently, a chain reaction could occur, requiring prolonged and intensive efforts to bring under control — this type of failure reaction is known as thermal runaway.
Because of residual heat inside the internal battery components, electric vehicle (EV) and HEV batteries have been reported to reignite for hours and even days after the initial fire is extinguished. Owing to the battery cell chemistry, these fires can reach temperatures of 5,000°F, significantly higher than the average temperatures of 1,500°F anticipated during a gasoline-powered vehicle fire.
These higher temperatures signify that the fire is more likely to spread to adjacent vehicles, structures and any nearby stored combustibles. The extreme temperatures also expose the parking garage structure to a level of heat that can cause structural weakening — or even failure — of steel and concrete. Moisture inside the concrete will vaporize and expand, which can create a condition called spalling (i.e., pieces of concrete are dislodged by the expanding water vapor, creating pits and cracks).
In comparison to gasoline-powered vehicles, EV and HEV batteries can add hundreds and even thousands of pounds to the vehicle weight; for example, a Tesla Model 3 weighs approximately 600 pounds more than a Honda Accord.
Therefore, it is critical that parking garages be designed to account for increased weight as EVs and HEVs continue to grow in popularity. Over the past 5 years, car shopping source Edmunds estimates weight has increased by 600%.
There are several factors that contribute to the growing number of EVs driven by consumers and, therefore, parked in parking garages. Green initiatives drive companies to make environmentally conscious changes and convert more of their fleets to EV and hybrid platforms. As technology improves and prices for EVs decrease, making these vehicles more affordable, it can only be expected that EV sales will continue to rise through 2025 and beyond.
Material fire protection hazards
The increasing availability and adoption of EV and HEV technology is not the only technological advancement that is reshaping the hazard landscape of parking garages. Gasoline-powered vehicles are also implementing technological changes that are significantly impacting parking garage fires — specifically the increasing use of plastics and rubber materials.
While these materials lighten vehicle weight and increase safety, the plastics are replacing many historically noncombustible materials in automobile manufacturing, primarily metals. These high concentrations of plastics and rubbers can create a vehicle fire that is more challenging that older-generation metal car parts that were both more difficult to produce but also heavier.
Reportedly, car fuel tanks made of molded plastic have melted when exposed to heat from a fire, causing the fuel inside to be released. Parking garages are designed with sloping floors and/or open drainage grates. When burning fuel is released, it can be conveyed away from the origin vehicle to expose additional vehicles; this concern is adding to fire protection challenges.
Finally, vehicle size contributes to larger fire loads. Cars and trucks are becoming larger and are thereby incorporating larger amounts of flammable materials, such as plastics and rubber. Plus, larger cars require larger fuel tanks.
How facility technology is changing
Parking garage technology is also changing. Urban parking garages are being redesigned as property owners struggle to maximize their available area to increase profits. To begin with, parking spaces are tighter and narrower, allowing fires more of an opportunity to spread to adjacent cars.
Additionally, more technological advances are being included in parking structure design, such as car stackers and automated parking systems, which can drastically change the hazard profile. Car stackers can create situations where cars stored on upper levels create an obstruction, thereby preventing fire protection systems from reaching intermediate or lower-level vehicles. Were a fire to occur in a car stacker, there is considerable risk that the stacking structure could be compromised by heat exposure and then catastrophically fail.
Another significant change includes the addition of EV charging stations, which has been outlined in some codes, including International Building Code (IBC) Chapter 4. While convenient for people who drive EVs, the stations increase protection challenges because they can store substantial amounts of power. If involved in a fire, it can be difficult to prevent reignition until the power storage systems are completely discharged; up to 30% of EV battery fires occur during charging. While facility owners want to offer these systems as a convenience to potential customers, it is at the price of increased fire risk.
However, the omission of battery charging stations does not eliminate the risk of EV fires in parking garages, as there have been reports of spontaneous combustion of EVs in these structures.
In some places, building owners will opt to include photovoltaic panels to reduce the costs of providing EV vehicle charging stations. These panels are typically constructed of plastic materials and the electrical connections introduce new potential risk pathways where short circuits and electrical faults could result in fires.
How changing technology impacts fire protection
Modern gasoline-powered vehicles and EVs/HEVs both introduce some additional ventilation concerns. Not only does the excess heat from these more challenging fires need to be vented away from the structure, but both vehicle types contain higher quantities of metals that can result in faster buildup of toxic products of combustion laden with heavy metals and other toxic byproducts.
While investigating these increasing challenges for protecting vehicle garages, several stories have been reported about garage fires that took days to control and even resulted in structural collapses. As a result, the NFPA has instituted major changes. Although these changes were introduced in the 2023 edition of NFPA 88A: Standard for Parking Structures and the 2022 edition of NFPA 13: Standard for the Installation of Sprinkler Systems, the jurisdictional adoption can lag by several years.
For this reason, in many jurisdictions, these requirements may not have been enacted or may be newly enacted; for property owners, authorities having jurisdiction and builders, there may still be some significant growing pains.
Property owners of existing garages are experiencing increasing pressure from the public to provide battery charging options and may not be fully aware of how these charging stations affect the level of risk in the event of a fire.
Active fire protection systems
Previous editions of the NFPA codes allowed open parking garages to omit sprinkler protection because it was expected that the openness of the garage would allow the heat and toxic products of combustion to freely vent into the atmosphere, thus lowering the risk of structural damage. It was also expected that this venting would help maintain visibility to ensure occupants had adequate time to exit the structure, even in the absence of sprinkler protection.
However, the more aggressive fires resulting from EV battery technology, HEVs and increased use of rubbers and plastics effect more than just the heat release rates — the production of toxic smoke is also significantly increased. Out-of-control garage fires, even in open garages, were resulting in injuries and even structural collapse and a risk for fatalities.
As a result, the 2023 Edition of NFPA 88A now requires sprinkler protection; however, the requirements are not retroactive, so existing open parking garages not equipped with sprinkler protection will be grandfathered and allowed to remain operational as they were constructed. (These requirements do not impact garages built as part of one- and two-family homes; however, new garages attached to multifamily dwellings are not excepted.)
NFPA 13 now requires a more robust sprinkler density in parking garages, beginning with the 2022 edition. Under earlier editions of the code, parking garages were considered ordinary hazard group 1 occupancies requiring a sprinkler density of 0.15 gallons per minute (gpm) per square foot over a design area of 1,500 square feet.
In the latest edition, the minimum fire sprinkler density allowed for a parking garage or an automobile showroom is an ordinary hazard group 2 density, which requires a minimum of 0.20 gpm per square foot over a 1,500-square-foot design area. Where dry-pipe sprinkler systems are required to accommodate for freezing potential, the design area would require a minimum 30% increase over the prescriptive design area for wet-pipe sprinkler systems.
NFPA 13 also included guidance in the appendix for car stackers up to two levels beginning in 2016 recommending extra hazard group 2 density if ceiling only sprinkler protection is provided. However, this does not preclude performance-based approaches to sprinkler system design for car-stackers based on the latest research available which may reduce the required ceiling densities where intermediate level sprinklers are provided to overcome the challenges of upper-level cars shielding lower levels from sprinkler discharge.
FM, a commercial property insurer, takes these increased sprinkler protection requirements for parking garages even further. Under new guidelines, parking garages are now reclassified from a hazard category of 2 to a hazard category of 3. This means that, under FM recommendations, a parking garage would require a minimum of 0.30 gpm per square foot over 2,500 square feet for a wet-pipe sprinkler systems to meet the requirements for extra hazard group 1 according to NFPA 13 — representing spaces nearing the top level of fire severity. The design area would increase to 3,500 square feet for dry-pipe sprinkler systems.
Even if a jurisdiction does not adopt NFPA 88A, parking garages are still held to the IBC, which removed the sprinkler exception for open parking garages. All parking garages are now defined as group S-2 moderate hazard storage occupancies and, as a result, all new parking garages greater than 55 feet in height or with a fire area greater than 48,000 square feet are required to be fully sprinkler protected.
Following suit, the 2024 editions of both NFPA 1: Fire Code and NFPA 101: Life Safety Code also both require all new parking garages to be fully sprinkler protected and do not include any exceptions based on height or square footage. Local codes may trigger protection upgrade requirements if existing parking garages are modified to add car stackers or EV charging stations.
These changes may also have ripple effects that should be expected to impact the project budget for new parking garages. For example, the more robust sprinkler design densities may drive increasing needs for fire pumps in parking garages (fire pumps increase the pressure of a water source when that source is not adequate). The addition of fire pumps and new requirements for mechanical ventilation may affect power requirements.
In areas of the country subject to freezing temperatures, it may be necessary to install dry-pipe sprinkler systems and provide heated enclosures for associated dry-pipe valves. Even considerations for the clear space between adjacent parking decks may need to be considered because adding sprinklers may reduce the available clear height, thereby limiting the height/size of vehicles that can safely navigate a parking garage without mechanically impacting the sprinkler system and causing damage or flooding. All of these considerations can be expected to impact the overall building design and construction costs.
Because EV and HEV fires can take an exceptionally long time to extinguish, they require vast quantities of water (compared to their gasoline-powered counterparts). As such, parking garages may require longer-duration water supplies and increased fire flow requirements in the future. In more rural areas, this may constitute improving the water supply to sites where new garages are being built, or in some scenarios, even considering the addition of water storage tanks.
The earlier 2019 edition of NFPA 88A had included new mandates for mechanical ventilation for enclosed and underground parking garages. This mechanical ventilation must be installed in accordance with NFPA 90A: Standard for the Installation of Air-Conditioning and Ventilating Systems and the ductwork must be constructed of noncombustible material. The latest 2023 edition added new requirements for ventilation, including a control system to turn fans off when fire suppression systems are activated, thereby necessitating an interface between automatic fire protection systems and fire detection and alarm systems with the mechanical ventilation systems.
Passive fire protection systems
In addition to the active fire protection systems — fire sprinklers and mechanical ventilation — there is also a need to consider passive fire protection in parking garages. Large open areas with multiple interconnected levels allow unimpeded pathways for toxic smoke to spread. Where parking garages are attached to or are underneath occupied buildings (of a different occupancy), there is the potential for spread of fire gasses through shafts such as elevators and stairs. Generally, dividing a parking garage into smaller fire compartments negatively impacts the flow of traffic through the garage; however, opportunities and obligations to design parking facilities with consideration given to compartmentation must not be overlooked.
Fires in vehicle parking structures have become more challenging for multiple reasons. Modern cars are built with larger amounts of plastics and rubber materials, which are flammable. In addition, EV and HEV fires present new and unique challenges owing to the intense heat produced and the risks posed by thermal runaway.
The extreme heat release rates, along with the heavier weight of EVs and HEVs, can negatively impact the structural integrity of vehicle parking structures, thus increasing the danger to civilians and firefighters alike. Fire and building codes are being revised and updated in response to these automotive technology changes; but, as with most reactive code changes, it will take time to fully understand all the inherent risks and to develop industry best practices. It is always important to involve a fire protection engineer early in the design process to ensure that facility design is following new code requirements.
