The prototype sprays the cryogenic liquid directly on burning vegetation. Liquid nitrogen rapidly vaporises when exposed to heat, cooling the fuel while displacing oxygen around the flames. Laboratory tests have shown that the combined effect can suppress fires involving pine needles and other combustible material found on forest floors.
The machine remains at the experimental stage and has not been deployed against an uncontrolled wildfire. Researchers are testing whether the technology can be scaled, transported safely and operated across the difficult terrain, extreme heat and unpredictable winds encountered during wildfire emergencies.
Yiannis Levendis, a professor of mechanical and industrial engineering at Northeastern, is leading the project with students Hayden Hishmeh and Aobo Liu. The current robot resembles a compact cylindrical container mounted on all-terrain caterpillar tracks, with a hose used to direct the liquid nitrogen.
Levendis began exploring the firefighting potential of liquid nitrogen after using it on burning tyre particles during a laboratory experiment in 2008. The flames were extinguished almost immediately, prompting research into whether the same principle could work on vegetation fires and persistent hotspots.
The approach is designed primarily for early intervention rather than confronting a large, fast-moving fire front. Small robots could be sent into locations considered too dangerous for firefighters, including steep slopes, areas with falling trees or ground containing smouldering material that may reignite.
The vehicles could be remotely controlled or eventually operate with greater autonomy. Thermal cameras and other sensors could help them identify heat sources, navigate around obstacles and direct the spray towards the most active parts of a fire.
Researchers believe robotic systems may be particularly useful during the mop-up stage, when crews search burned areas for concealed embers. Hotspots beneath leaves, branches or soil can survive after visible flames have disappeared and later trigger another outbreak, especially when wind speeds rise.
Liquid nitrogen also offers an environmental advantage because it evaporates into nitrogen gas, which already forms most of Earth’s atmosphere. It does not leave the chemical residue associated with some wildfire retardants, which can enter waterways or affect soil when applied in large quantities.
However, the cryogenic material creates major logistical and safety challenges. Liquid nitrogen must be stored at about minus 196 degrees Celsius in specially insulated tanks. Hoses, valves and pumps must withstand extreme cold, while operators require protection from cold burns, oxygen displacement and pressure created as the liquid turns into gas.
Transporting sufficient quantities into forests would also be more complicated than supplying water from local sources. The prototype’s effectiveness will depend on how much liquid nitrogen it consumes, how long its tank lasts and whether refilling equipment can be positioned close to an active incident.
The technology may therefore be more practical for targeted suppression than blanket application. A robot could treat a defined hotspot with a precise spray, while aircraft, engines and ground crews continue using water and retardant against larger fire areas.
The project received funding from the Gordon and Betty Moore Foundation, enabling the team to acquire equipment and build the robotic platform. Controlled tests have used materials associated with forests in the western United States, where dry pine needles, sticks and scrub can allow ground fires to spread rapidly.
Wildfires burned more than 5.13 million acres across the United States in 2025, increasing pressure on emergency agencies to find technologies that reduce response times and limit human exposure. Robots and drones are already used for mapping fire perimeters, detecting hotspots, carrying sensors and conducting aerial ignition during prescribed burns.
Active robotic suppression remains less established. Existing firefighting machines generally rely on water or foam and are more commonly designed for industrial facilities, tunnels, warehouses and urban incidents. Applying cryogenic suppression to wildland fires introduces a different method based on rapid cooling and oxygen displacement.
The Northeastern team has also considered larger delivery systems, including vehicles comparable in size to fire engines. Any expansion would require extensive field trials, coordination with firefighting agencies and engineering assessments covering storage, vehicle weight, range, reliability and environmental conditions.
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