Radium Engineering offers top of the line fuel delivery solutions for the motorsports market, including fuel cells. Many consider fuel cells as a simple metal container, when in fact a proper motorsports fuel cell is more complex for safety purposes.  A basic aluminum, stainless or mild steel container can easily leak in the event of a collision and could lead to a dangerous fire situation. Even a minor fender bender or the flexing of the chassis during hard driving could create enough force to distort and crack the metal container, resulting in fuel spillage. Fuel weighs nearly 7lbs per gallon, and with a 15 gallon fuel cell that is 100lb of fuel sloshing around inside the metal box, flexing the walls and straining the welds. When that much weight is subject to g-loading from aggressive driving, the resulting forces are very large and can damage poorly designed metal containers. Also, chemical compatibility, weld quality and corrosion are concerns when using a plain metal container for fuel storage. In short, Radium does not recommend these types of fuel containers on performance cars and trucks.

Fuel cells used in motorsport racing often require FIA or SFI certification to ensure safety requirements are met. The guide below helps explain how a fuel cell works and why certification is necessary.
What is a Fuel Cell?
As shown, fuel cells are generally comprised of three components: the outer shell (enclosure or can), the bladder (where fuel resides) and foam baffling.
Radium Engineering fuel cell enclosures are made from aluminum, but others are generally made from steel. The enclosure is the first part of the cell to absorb damage and to help prevent a serious catastrophe. This layer is similar to the construction of a helmet. The outer enclosure aids in safety but is not the most critical part. FIA specs do not cover the outer can, only the bladder. Other governing bodies do require certain outer can thicknesses. For instance, SCCA requires a fully enveloped enclosure comprised of 0.036” steel or 0.059” aluminum.
The fuel cell bladder protects from fuel spills. The bladder holds fuel and must be resilient against impacts, punctures, and tears. The material also needs to be flexible enough to prevent cracking or fuel leakage in the case of impact. These requirements have led to the development of different high-tech materials used in the industry.Radium Engineering chose to only focus on molded polymer bladders, as they have the best chemical compatibility, are a great value, and still meet all the structural testing requirements put forth by SFI and FIA.

The foam baffling is basically a large sponge inside the fuel cell. It serves several purposes. If catastrophic failure were to happen, this porous foam helps absorb the fuel and prevent an explosion. It helps suppress explosion potential by preventing fuel vapor buildup inside the cell. As an added benefit, it helps prevent fuel slosh which can contribute to fuel starvation. Fuel cell foam is a wear part and should be inspected periodically to ensure it is in good shape. Loss of elasticity or degredation of any kind are signs that it needs to be replaced.
What is FIA?
The Federation Internationale de l’Automobile (FIA) is a 115 year old international organization that promotes road safety around the world and creates rules and regulation governing all forms of motorsports. It's most prominent role is in the licensing and sanctioning of Formula One, World Endurance Championship, World Rally Championship and various forms of sports car and touring car racing.
FIA Homologation
For the safety of the driver, FIA homologation (certification) is required in many forms of racing. This covers many safety related components including fuel cell bladders. FIA has a few distinct classifications regarding fuel bladders: FT3, FT3.5, and FT5. There are other standards required by other sanctioning bodies, but FIA is the gold standard.
All of the ratings clearly define the requirements for materials, construction, and testing. The only difference between the ratings is the strength of the bladder material. All tests utilize the same procedures but the levels of certification are based on test results. FT3 is the lowest level requiring the lowest minimums while FT5 requires the highest.
For example, Formula-1 requires FT5, but SCCA requires FT3 (although FT3.5 and FT5 are also acceptable.) Check with your sanctioning body to see what requirements your vehicle must meet.
Certification Expiration
Fuel cell certification expires 5 years after the date of manufacture. Check the label on the fuel cell bladder for an expiration date.
Fuel Cell Deterioration
Many factors contribute to the bladder breaking down overtime. Anything from heat, UV light, vibrations, and the fuel itself will eventually break down the elastomers. Water and alcohol cause deterioration more rapidly. Fuel cells should be regularily inspected and replaced as needed.
Fuel cells generally require some level of maintenance. Regular maintenance ensures it will last the full 5 years, and longer in non-certified applications.
Maintenance tips: The fuel cell should be drained whenver the vehicle is stored for a long period of time. This will extend the life of the fuel cell. Alcohol is most damaging to the foam. Proper care of this part of the cell is crucial for maintenance. Foam breaks down over time and particles can clog the fuel system. It is ideal to periodically replace the foam in the cell to increase cell longevity. Always follow the guidelines included with every Radium Engineering fuel cell.
Inspection: While you are replacing the foam, always inspect the bladder for any signs of wear, damage or degredation.

To conclude, metal box style "fuel cells" are prevalant on the discount market, however, they offer little to no engineering or regard to safety. The added cost of a bladder-style fuel cell can be easily justified in the event of any type of incident.