How Denver International Airport cut PFAS levels in legacy firefighting equipment
Legacy firefighting foam under new environmental rules
Firefighting vehicles at major airports have historically relied on aqueous film‑forming foam (AFFF) to suppress fuel fires. For decades, this was a regulatory requirement at many airfields. However, AFFF contains per‑ and polyfluoroalkyl substances (PFAS), which have raised growing environmental and public health concerns.
In August 2021, the State of Colorado restricted the sale, manufacture, and distribution of PFAS‑containing firefighting foam. These changes created a complex challenge for airport operators and fire departments on how to comply with new environmental regulations while maintaining emergency response readiness and meeting federal aviation safety requirements.
At Denver International Airport (DEN), the issue was beyond just replacing foam supplies. PFAS residues remain inside fire truck foam systems and trailers that had stored or circulated AFFF for years. Without proper decontamination to prevent release of equipment-bound PFAS, these vehicles could continue to pose environmental risks during maintenance, training, or emergency use. The client needed a solution that could measurably reduce PFAS contamination inside existing vehicles, manage residual PFAS‑containing waste responsibly, and be delivered within operational and regulatory constraints.
A verified, compliant decontamination program
We supported Denver International Airport’s Sustainability Division and the Denver Fire Department to evaluate and implement a technically effective and cost‑conscious vehicle decontamination program.
The work focused on cleaning the interiors of Aircraft Rescue Fire Fighting (ARFF) trucks and foam supply trailers. We provided technical expertise, decontamination oversight, sampling support, and overall project management. The program compared PFAS concentrations before and after cleaning to evaluate performance to lower the risk of relying on assumptions or conventional visual inspection alone.
As part of the process, PFAS‑containing AFFF was off‑loaded from each vehicle, stored in other containers pending disposal, and replaced with a fluorine‑free foam that meets applicable specifications by the Federal Aviation Administration (FAA) and the military specification (MILSPEC).
By integrating decontamination, analytical verification, and waste management into a single coordinated effort, the project addressed regulatory compliance and operational continuity at the same time.
Managing persistent PFAS in closed systems
Decontaminating fire truck foam systems presents technical challenges beyond standard equipment cleaning. PFAS compounds are persistent, can adhere to internal surfaces, and are difficult to remove using conventional water rinses alone.
For this project, AECOM worked with a subcontractor to apply a cleaning system using commercially available organic flocculant designed to bind many PFAS compounds. The cleaning agent was mixed with hot water and recirculated through the vehicles’ foam piping systems in multiple cycles. Each vehicle underwent repeated rinse cycles, followed by a final clean‑water rinse.
The generated rinsate during the process was captured, stored in large frac tanks, and transported offsite for disposal. Analytical testing of pre‑ and post‑cleaning effluents was conducted using the standard EPA Method 1633A and in accordance with Colorado Department of Public Health and Environment requirements. This level of analytical verification was essential to demonstrate that the cleaning process achieved meaningful PFAS reduction.
Measurable PFAS reduction and operational readiness
The decontamination program was carried out between 2023 and 2025, with field activities beginning in October 2024. Eleven ARFF fire trucks and nine vehicles used for structural fires were cleaned as part of the effort.
Measured PFAS removal rates averaged 98.72% across vehicles.
“As DEN continues its efforts to become the greenest airport in the world, it’s our duty and responsibility as leaders in the aviation industry to ensure the safety of our fire personnel, employees, surrounding communities and the environment,” DEN CEO Phil Washington said. “I’m proud to say DEN has taken proactive measures and is one of the first airports in Colorado to lead the way.”
Beyond the technical results, the project provided practical value to the client. Early action allowed DEN to secure a compliant disposal pathway aligned with project schedules and waste volumes. The work also supported the airport’s transition to fluorine‑free firefighting foam while maintaining fire safety readiness.
A replicable model for managing legacy PFAS risks
As PFAS regulations continue to evolve, many of our clients face similar challenges with legacy equipment and infrastructure. This project demonstrates that existing firefighting vehicles and other assets can be effectively decontaminated, rather than replaced, using a structured, data‑driven approach.
The combination of verified PFAS reduction, compliant waste management, and operational coordination provides a flexible model that can be applied at other facilities navigating the shift away from PFAS‑containing foams. For DEN, the work supports long‑term environmental stewardship while preserving critical emergency response capability. For our other clients with contaminated assets, this project demonstrates a flexible “treatment train” framework with multiple options based on their objectives.