Fire Hazard

• In the fuel cell, a thin wall separates the hydrogen and oxygen gases. This wall has a thickness of approximately 20 to 30 micrometers. Since the wall is extremely thin, it could break down easily. As a result, the two gases (hydrogen and oxygen) could mix in an uncontrolled manner. This could lead to an explosion in the fuel storage compartment or the fuel supply lines. This event is detectable by modern equipment and thus the explosion could be avoided by shutting off the gas lines and preventing any sparks from the fuel cell. However, the danger cannot be completely discounted.
  
  

Handling Problem

• Liquid hydrogen is very cold and, therefore, difficult to work with. It is a challenge to handle liquid hydrogen at a temperature of approximately minus 420 degrees. In order to withstand the cold temperatures, hydrogen fuel tanks must have a combination of vacuum barriers and "super-insulation" which can withstand extreme cold temperatures. In consequence, the valves, fittings and seals which are needed in such installations are difficult to maintain.
  
  

Backfiring

• If hydrogen leaks from its storage space and builds up in an enclosed space, it could lead to an explosion. This is possible if hydrogen and oxygen mix outside the cylinder of an engine, resulting in backfiring. This explosion could travel very quickly due to a high flame velocity.
  
  

Additional Risks

• When stored as liquid, hydrogen fuel also poses the risk of inflicting cold burns (because of the extreme cold temperatures). Storing hydrogen as liquid also adds the possibility of an explosion from rapidly expanding vapors in the fuel tank which can be caused by a malfunctioning pressure relief valve. Moreover, liquid hydrogen spills at a very fast rate, much faster than gasoline spills.
  
  

Future of Hydrogen Cars

• In order to fully understand and address the safety risks associated with hydrogen cars, further testing and investment in this area would be needed. As more research is completed, the safety concerns will likely be resolved and hydrogen cars will become a viable mean of transport.