Fire Safety for Electric Vehicles and Other Modern Vehicles in Parking Structures
In spite of the global supply chain issues and loss of vehicles in the Felicity Ace cargo ship fire, the sales of electric vehicles (EVs) has been on the move, hitting 6.6 million in 2021, which is more than triple their market share from two years earlier. While this might be good news for our environment, it also brings unique fire challenges to both first responders and fire protection designers.
The lithium-ion (or similar) batteries inside of these vehicles fail and burn in a much different way than internal combustion engine (ICE) vehicles. When lithium-ion batteries fail, they go through a process called thermal runaway, where a single cell failure can cause the production of heat and oxygen as well as flammable and toxic gasses. This then spreads to adjacent cells causing potential rapid fire growth or explosion.
To give us some perspective about the size of this issue, it is estimated that there are around 16 million electric cars on the road worldwide, and studies have identified nearly 300 EV fires globally between 2010 and 2022. Compare this with ICE vehicle fires and we find that EV vehicle fires are less common of an occurrence, but more complicated of an event, since EVs fires can last longer and have the potential for electrical shock and reignition. While a majority of vehicle fires occur on the road, it’s the fires that occur in parking structures that lead to large economic loss as evidenced by recent fires at Liverpool’s Echo Arena (UK) and at the Stavanger Airport (Norway).
What makes a parking garage or parking structure unique?
Parking garages, often called parking structures in code books, are a unique type of occupancy. They can be located underground or above ground and are usually located in congested urban areas where large open parking lots aren’t feasible. They can be public or private and store anything from motorcycles and cars to trucks and buses. There might be access for each vehicle to enter and exit or there might be vehicles covering the entire floor area.
There can also be several different types of technology integrated into parking structures, such as car stackers or automated parking systems which store and retrieve vehicles without a driver. These types of technologies increase the efficiency of the space being used but also increase the potential hazard by placing vehicles closer together.
With all of these variables already existing in parking structures, the introduction of electric vehicles and electric vehicle charging stations adds more considerations that need to be made when designing and protecting these occupancies.
What do the codes say?
What do the current codes and standard say about electric vehicles in parking garages? While they don’t go into much detail, there are some requirements in NFPA 70®, National Electrical Code® (NEC®) and NFPA 88A, Standard for Parking Structures, that address certain safety concerns.
The NEC is the go-to code when looking to protect people and property from electrical hazards and so, as appropriate, it has requirements for installing EV charging stations, or “Electric Vehicle Supply Equipment,” as they call it in the code.
When conducting service load calculations, Article 220 requires EV Supply Equipment to be calculated at either 7,200 watts or the nameplate rating of the equipment, whichever is larger. This is to ensure the electrical supply will be able to handle the extra load put on by EVs charging.
Most of the other requirements for electric vehicle charging stations are going to be located in Article 625, Electric Vehicle Power Transfer System. While this article contains many requirements, some of the highlights include requirements for EV charging equipment to be listed, to have a disconnecting means, and for charging coupling to be a minimum distance above the ground.
The other major standard that addresses EVs in parking structures is NFPA 88A. Similar to NFPA 70, it requires the charging stations and equipment to be listed but it gives more details into the exact listing standards it needs to meet.
- Electric vehicle charging stations need to be listed to UL 2202, Standard for Electric Vehicle (EV) Charging System Equipment.
- Electric vehicle charging equipment need to be listed to UL 2594, Standard for Electric Vehicle Supply Equipment.
- Wireless power transfer equipment needs to be listed to UL 2750, UL LLC Outline of Investigation for Wireless Power Transfer Equipment for Electric Vehicles.
Impact of modern vehicles
The introduction of EVs into the ecosystem isn’t the only thing to consider when looking at how to properly design and protect parking structures. The fire characteristics of modern vehicles are also changing to include more plastics and other combustibles than ever before. While this benefits the fuel economy and lowers vehicle price, it increases the fuel load and fire growth we see in parking garages. A recent Fire Protection Research Foundation report dives into details about the fire hazard modern vehicles represent to parking garages and marine vessels. In addition, there have also been updates to various standards in response to these increased fire hazards found in parking garages.
The 2022 edition of NFPA 13, Standard for the Installation of Sprinkler Systems, for example, has changed to increase the recommended hazard classification for parking structures from an Ordinary Hazard Group 1 to an Ordinary Hazard Group 2. The effect is a 33 percent increase in the design density, moving from 0.15 gpm/ft2 to 0.2 gpm/ft2.
As of January of 2021, FM Global data sheets have also increased the hazard category for parking garages and car parks from a Hazard Category 2 to a Hazard Category 3.
New to the 2023 edition of NFPA 88A, all parking garages are now required to have sprinkler systems installed in accordance with NFPA 13. Prior to this edition, sprinklers didn’t have to be installed in open parking structures.
While technology is constantly evolving, so are NFPA codes, standards, trainings, research, and other resources. The ever-growing presence of lithium-ion batteries in our day-to-day lives are changing the fire characteristics of our built environment. Fire protection professionals need to be able to stay on top of these changes to ensure the safety of people and property. For more information on the resources NFPA provides relates to electric vehicles, check out nfpa.org/EV.