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When evaluating aboveground steel tanks for fuel, oil, and lubricant storage, three commonly specified designs frequently enter the discussion: Fireguard®, Flameshield®, and STI-F921®.
All three are designed to support safe aboveground storage of flammable and combustible liquids, but they are not interchangeable. Each is built for a different balance of fire protection, containment, compliance, and site demands. One thing all these tanks have in common is a two-year warranty backed by STI. But what makes them different?
This guide explains where each tank fits best so you can more confidently match the product to the application.
Fireguard®: Best When Fire Protection Is the Top Priority
Fireguard® tanks are designed for applications where enhanced fire protection is the primary concern. These tanks feature double‑wall, fire‑protected steel construction with integrated thermal insulation, allowing them to meet UL 2085 fire‑resistance standards while also providing built‑in secondary containment.
Design and Performance Distinctions
This design is built to UL 2085 standards, which has a higher fire-protection standard than UL 142. That distinction is often critical in site conditions where fire code requires enhanced fire resistance due to reduced separation distance, exposure protection, or enhanced fire resistance. In short, Fireguard is usually the tank you evaluate when the project team starts by asking, “What level of fire protection is required here?”
Learn more on UL 2085 vs UL 142 standards
Common Applications
Think about a fleet maintenance facility operating inside a busy city service yard. The site is close to buildings, vehicle traffic, and other active operations. The owner needs built-in secondary containment, but local fire code also places a premium on stronger fire-resistant construction.
In that kind of setting, this option is often the better fit because it combines containment and higher-level fire protection.
Other common applications for this tank include:
- Hospitals and healthcare campuses
- Schools and municipal facilities
- Airports and transportation yards
- Generator fueling in code-sensitive locations
- Industrial sites with strict fire marshal review
To learn more on Fireguard®
Flameshield®: Best When You Need Double-Wall Construction with Fire-Tested Performance
Flameshield® tanks are double‑wall, all‑steel tanks with built‑in secondary containment and 2‑hour fire‑tested performance. They feature a tight‑wrap double‑wall design, meet UL 142 standards, carry STI and Southwest Research Institute labels, and are available in sizes up to 30,000 gallons.
Design and Performance Distinctions
This tank fills an important middle ground because it offers more fire-related performance than a standard double-wall tank whose focus is containment alone. While Flameshield tanks are fire-tested, they are not fire‑protected designs under UL 2085 and therefore do not provide the same passive fire-resistance duration. This specification is often considered when the key decision becomes: How much fire‑tested protection is needed per local code without stepping into a full fire‑rated design?
Common Applications
Consider a contractor yard or oil jobber branch that needs bulk fuel storage for daily operations. The buyer wants double-wall containment and recognized fire-tested performance, but also must balance installation cost, site layout, and lead time.
That is where this option can make sense. It combines secondary containment and 2-hour fire-tested performance with double-wall construction when code requires more than standard containment, but not full fire-rated protection.
Other common applications for this tank include:
- Fleet distribution terminals and bulk plants
- Equipment rental and heavy equipment yards
- Manufacturing and industrial facilities
- Marinas and waterfront fueling locations
To learn more on Flameshield®
STI-F921®: Best When Containment and a Practical, Cost-Efficient Solution Leads the Decision
STI-F921® is a double-wall steel tank designed to provide impermeable secondary containment in support of EPA SPCC planning and UL 142 requirements. It is often a strong fit when the main priorities are secondary containment, environmental compliance, and cost efficiency.
Design and Performance Distinctions
This tank is especially useful when a site needs a double-wall tank to support spill prevention and environmental objectives but does not require the higher fire-protection profile associated with Fireguard® or the fire-tested emphasis of Flameshield®. This is often the specification considered when the primary question is: How do we meet containment requirements efficiently and confidently?
Common Applications
Picture a private commercial facility with a standby generator, or a remote operations site storing diesel for equipment. The operator needs reliable aboveground storage, wants built-in secondary containment, and must meet spill prevention expectations.
In that situation, it is often the practical answer because it emphasizes containment and compliance without overbuilding for a fire rating the site may not require.
Other common applications for this tank include:
- Backup generator fueling
- Agricultural operations
- Rural commercial properties
- Bulk lubricant or petroleum storage
- Sites focused on SPCC planning and environmental safeguards
To learn more on F921®
Side-by-Side Summary
Here is the simplest way to compare the three:
- Fireguard®: best for fire-protected, thermally insulated construction
- Flameshield®: best for double-wall construction with 2-hour fire-tested performance
- STI-F921®: best for double-wall containment where SPCC focus
The Quick Decision Guide: Which Tank Is Right?
- If fire code is tight or space is constrained → Fireguard®
- If you want fire-tested performance without full fire rating → Flameshield®
- If your priority is containment and compliance at lower cost → STI-F921®
Questions to Ask Before Choosing a Tank
1. What level of fire protection does the application require?
Some projects call for fire-protected construction, while others are focused more heavily on containment and environmental planning.
2. Is built-in secondary containment required?
All three address containment, but they do so in different ways and to different performance priorities.
3. Which code or compliance path is shaping the decision?
Applicable fire code, environmental requirements, owner standards, and local expectations all influence the best fit.
4. How much site flexibility do you need?
Tank orientation, coatings, bulkheads, and other options can affect installation, approvals, and long-term usability.
One Important Reminder: The Site Always Has the Final Say
No tank comparison is complete without this point: local code requirements matter.
Tank selection should always be confirmed with the local authority having jurisdiction, along with any environmental, permitting, insurance, and fire code requirements tied to the project.
That is why the real question is not about which tank is the best. It is: Which tank is best for this site, this application, and this level of compliance?
Common Mistakes Buyers Make
Choosing based on price alone
Lower upfront cost can lead to higher total project cost when fire‑rating, permitting delays, or site constraints are overlooked.
Assuming all double‑wall tanks are equivalent
Double‑wall construction meets containment needs, but fire resistance, testing standards, and code acceptance vary significantly by design.
Not confirming local code early
Fire marshal and AHJ requirements can dictate tank type, spacing, and protection level—discovering that late often forces redesigns or replacement.
Overbuilding when not required—or underbuilding when it matters
Specifying more fire protection than needed can waste budget, while under‑specifying can create approval hurdles and safety risks.
Need Help Choosing the Right AST?
Explore the Choosing the Right AST blog, consult your local fire authority to confirm fire and environmental code requirements, or connect with your Newberry Tanks Regional Account Executive for one-on-one guidance.
To learn more on Knowledge Center
Why Newberry Tanks?
Newberry Tanks helps simplify compliance with fast delivery, order guidance, kitting, and turnkey tank solutions to complete the install.
Newberry Tanks offers:
- 100 years of experience building at the source
- A large inventory of in-stock tanks and equipment
- Fast nationwide shipping
- An experienced team that understands real-world applications
For buyers who are balancing deadlines, approvals, and jobsite realities, that support can matter just as much as the tank itself.