As the world shifts toward cleaner energy solutions, hydrogen is emerging as a powerful contender to replace fossil fuels in our homes and cities. It burns clean, produces only water, and can be generated from renewable sources.
But there’s a catch.
Hydrogen is, in many ways, a restless element – lighter, more mobile and easier to ignite than natural gas and gasoline. So how do we make this fuel just as safe and dependable? At Canadian Nuclear Laboratories (CNL), the Hydrogen Safety Section within the Hydrogen Technologies Branch is tackling that exact question supported by multidisciplinary teams of engineers, scientists, and laboratory technologists. Their work doesn’t just focus on using hydrogen – it focuses on understanding it, predicting its behaviour, and controlling it long before it becomes a hazard.
Hydrogen may be the lightest element in the universe, but when it leaks, it doesn’t always behave as simply as we expect.
Using advanced “digital twin” simulations – highly detailed computational fluid dynamics (CFD) models – these teams study what happens when hydrogen or hydrogen blended natural gas leaks from pipelines in real-world environments, particularly in cities.
In open spaces, hydrogen rises quickly and disperses. But in urban environments, the buildings change everything.
Dr. Marco Zanoni, Ph.D., Research Scientist at CNL explains, “what surprises us most, is that hydrogen doesn’t always rise. If there are structures that trap it, it can stay in place – and that’s where it can become dangerous.”
Between structures, wind patterns can create what researchers call “urban canyons” – tight corridors where air circulates in loops rather than flowing freely. In these spaces, hydrogen can become trapped in recirculation zones, lingering close to the ground where people live, walk, and work.
These seemingly minor insights are critical findings in the research. They allow engineers and city planners to anticipate where hydrogen might accumulate and design infrastructure that prevents those risks before they ever materialize.
Even hydrogen blends – such as mixtures of up to 20% hydrogen with natural gas behave similarly to existing natural gas systems. But as concentrations increase, so does the need for smarter design and planning.
What Makes Hydrogen Different from Other Fuels?
Part of the challenge comes down to hydrogen’s unique physical properties.
Compared to fuels like methane or gasoline, hydrogen is extremely light, making it prone to leaking and dispersing quickly. It has a much wider flammability range and requires far less energy to ignite – even small static sparks can be enough. It can interact with materials, requiring specialized pipelines and storage systems – this is where the hydrogen technologies branch research comes into play.
“These characteristics don’t make hydrogen unsafe – but they do mean it must be handled carefully,” suggests Dr. Zhe (Rita) Liang, a Senior Research Scientist and Hydrogen Safety Section Head with CNL. “It’s not that hydrogen is more dangerous – it’s simply less familiar to the public. If you understand its behaviour and design for it properly, the solutions are already there.”
While some work focuses on predicting where hydrogen might go, other work is focused on what to do if it gets there.
Passive Autocatalytic Recombiner – PAR
CNL has developed technologies that remove hydrogen from the air before it ever reaches dangerous levels. At the heart of this work are devices called Passive Autocatalytic Recombiners (PARs), systems that act like silent guardians.
Instead of igniting hydrogen, they use specially engineered catalysts – materials that trigger chemical reactions – to recombine hydrogen with oxygen at very low concentrations. The result? Water vapour.
No flame. No explosion. Just a quiet conversion back to something harmless. These systems are entirely passive and don’t require power, human intervention, or activation.
“They just sit there,” Dr. Liang explains. “If hydrogen is present, they start working automatically.”
This makes them ideal as a fail-safe solution, especially in scenarios where power might be unavailable – such as during emergencies or in remote environments.
From Nuclear Safety to Everyday Applications
While recombiners are nothing new, their current uses represent a significant shift.
Originally developed for nuclear power plants, where preventing hydrogen buildup during accidents is critical, CNL researchers are adapting these same technologies for use in battery storage rooms, underground mines, hydrogen transport systems, industrial facilities and even for future hydrogen-powered residential applications.
Different designs – such as high-flow recombiners for exhaust systems or water-cooled versions for industrial processes – allow the technology to be tailored to specific environments.
And unlike traditional ventilation systems, which can be energy-intensive, these devices offer a low-energy alternative that works continuously in the background.
The double underline here, is that what makes hydrogen safe isn’t any single technology – it’s the combination of many.
CFD modeling helps predict where hydrogen could accumulate. Recombiners help remove it. Risk assessments calculate both the likelihood of leaks and their potential consequences, guiding engineers toward safer designs. Together, these layers form a comprehensive safety system.
“If you know the issues,” Dr. Liang adds, “you already have the solutions. The technology is ready – it’s about applying it properly and building the expertise around it.”
Despite its promise, hydrogen faces one major hurdle: public perception.
For many people, the word “hydrogen” still brings to mind historical disasters like the explosion of the Hindenburg airship. And while modern hydrogen systems are vastly more advanced, that trust takes time to build.
It’s the same path natural gas once followed.
Today, natural gas is widely accepted in homes – even though it is also flammable. Hydrogen, researchers believe, can reach that same level of trust. But only if safety comes first.
Making Safety the Foundation of Hydrogen’s Success
Hydrogen isn’t just a fuel of the future – it’s a fuel we’re learning to master today.
Through advanced modeling, passive safety technologies, and decades of expertise borrowed from the nuclear industry, a team of researchers at CNL are building the safety net that hydrogen needs to be a successfully joined energy superpower.
Because in the end, the success of hydrogen won’t just depend on how clean it is.
It will depend on how safe we make it – and how confidently we can use it in the everyday spaces where life happens.
This research is funded by Atomic Energy of Canada Limited’s (AECL) Federal Nuclear Science & Technology (FNST) Work Plan, which connects federal organizations, departments, and agencies to the nuclear science expertise and facilities we have at Chalk River Laboratories.
Under the FNST Work Plan, researchers at Canadian Nuclear Laboratories (CNL) carry out projects to support the Canadian government’s core responsibilities and priorities across the areas of health, safety and security, energy, and the environment.
