By Josh Miller, PE, CFPS – Fire Protection Engineer | Portland Office
The fire hazards associated with storing cars in parking garages have changed significantly due to modern automobile manufacturing methods and trends in parking garage design practices.
Fire Considerations of Electric Vehicles
Electric vehicles (EVs) are an emerging technology gaining in popularity and widespread adoption. While EVs have a relatively high plastic content (similar to ICEVs), the lithium-ion batteries used as a power source present a unique fire-fighting challenge. Lithium-ion batteries have proven to create long-burning and water-intensive fires that are difficult to contain. Additionally, lithium-ion batteries can re-ignite after the fire is initially controlled, which is a clear cause for concern for the responding agencies that may be unaware of this danger. The water required in both flow and duration to contain lithium-ion fires should be a consideration where fire-fighting methods rely on a finite water supply, such as a reservoir tank.
Use of Plastics in Automobile Manufacturing
In the highly competitive passenger automobile industry, manufacturers have quickly responded to customer concerns surrounding fuel economy. Manufacturing has adapted by increasing the use of plastic and synthetic materials in place of steel and aluminum, which reduces curb weight and cost. Plastic and synthetic content has increased dramatically in vehicle interiors and are also being used more frequently in exterior body panels and exterior trim. Plastics have exceptionally high heat release rates and potential fire energy, especially when compared to non-combustible alternatives like steel and aluminum. Most internal combustion engine vehicles (ICEV) manufactured today use high-density polyethylene (HDPE) plastic for the gas tank, a relatively weak fire barrier for the flammable gasoline inside the tank. Limited research on the topic suggests a multimodal increase in fire hazards due to the use of plastics in modern ICEVs.
Evolving Parking Garage Design
Along with changes to modern vehicles, parking garages have also undergone significant changes. Despite the consumer shift toward larger vehicles, modern parking garages tend to have narrower parking spaces than older garages. There is significant pressure on developers to maximize parking density in buildings, which is resulting in increased use of parking stackers that mechanically lift vehicles to take advantage of vertical parking space. The increased vehicle density leads to more fuel in smaller spaces. With tightly packed fuel loads, both horizontally and vertically, and large amounts of plastic, there is a serious risk of flame spread between vehicles during a fire event.
Planning for the Future
Substantial changes have occurred in vehicle manufacturing and parking garage design practices, but much of the testing that informs the current code is decades old. Although more interest and testing relating to these topics is currently in progress, more research is needed to understand the complex interactions that occur in a modern parking garage fire. Substantial changes have already been made to IBC codes and NFPA standards to address modern vehicle fire protection issues, but more changes are sure to come. In this time of transition, it is critical for building owners and design professionals to work with qualified fire protection engineers who understand the issues and changes affecting parking structure codes and standards.
Learn more about recently enacted changes to codes and standards that will be officially adopted by states in upcoming code cycles: Reassessing the Fire Hazard in Parking Structures