Hyundai's hydrogen-powered Nexo crossover is in trouble with the National Highway Traffic Safety Administration (NHTSA) due to suspected hydrogen gas leaks. As you might expect, this poses a fire safety risk that necessitates a recall.
While the NHTSA is concerned that the affected vehicles could become road-going Hindenburgs, there doesn’t appear to be any reports of accidents, injuries or fires. However, the relevant documentation filed with the agency does paint a scary picture.
Hydrogen tanks are under a tremendous amount of pressure relative to the typical tank holding gasoline. Anyone who has ever driven a hydrogen fuel cell vehicle knows that you actually have to secure the nozzle to the port like you’re filling up a space rocket. This requires that hydrogen vehicles have the ability to vent excess pressure to the atmosphere, necessitating some kind of release valve for safety. Sadly, this component is actually the source of the recall on select 2019-2024 Hyundai Nexo models.
From the Safety Recall Report:
The subject vehicles are equipped with a Thermally-activated Pressure Relief Device (“TPRD”) that vents hydrogen gas to the atmosphere to prevent over- pressurization of the hydrogen fuel tank in the event of overheating in the local area around the hydrogen fuel tanks. The TPRD is designed to vent gas through a glass bulb-type release mechanism that fractures when a specific operating temperature is reached. The glass bulb-type mechanism in the subject vehicles could prematurely fracture due to microcracks in the glass, which could lead to inadvertent discharge of hydrogen gas during normal vehicle operation.
The report makes it sound like you’d definitely notice this happening. A fractured TPRD bulb would quickly vent the hydrogen stored within the tank to the atmosphere, resulting in a “loud wind-rushing noise can be heard accompanied by a white fog-like cloud near the rear of the vehicle.” But even those missing the obvious physical signs would likely notice their fuel gauge dropping and the subsequent warning lights.
While it sounds like the system could leak hydrogen more slowly, the report focuses on a complete failure of the pressure relief device. Having this happen while driving would likely result in your scaring nearby vehicles and eventually finding yourself without enough hydrogen to get home. But the real danger seems to stem from the vehicle venting hydrogen in a closed environment where there’s a potential ignition source. Fires while on the road are not impossible but having a garage filled with the gas where there’s a spark could theoretically result in an explosion.
With the above in mind, Hyundai is recommending all Nexo owners park their vehicle outdoors and away from structures until the defect has been addressed. The recall went into effect earlier this month, with the Thermally-activated Pressure Relief Device (manufactured by Korea’s Youngdo Industry) being replaced by the automaker free of charge. Hyundai will provide owners of affected vehicles reimbursement for any out-of-pocket expenses incurred to obtain a remedy for the recall condition in accordance with the reimbursement plan submitted to NHTSA on February 22nd, 2024.
The issue is presumed to impact about 1 percent of the roughly 1,500 Nexo models involved in the recall. But vehicles manufactured after May 21st, 2024 won’t be included due to the company having already discovered the issue by then. Concerned owners can contact Hyundai directly or use the NHTSA database (using their VIN) to learn more.
[Images: Hyundai]
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