Data center construction spending in the United States hit $49.5 billion through April of this year — nearly four times the pace from the same period in 2025. More than 66 gigawatts of capacity is under construction across North America, with individual AI training campuses routinely drawing 100 to 500 megawatts of continuous power. This is the largest category of new industrial construction in the country.
Each of those facilities has a diesel backup system ready the moment utility power fails. The generators, day tanks, bulk storage, transfer pumps, fuel piping, and containment areas represent tens of thousands of gallons of fuel sitting inside or adjacent to some of the most expensive rooms on the planet. The backup power system protects the data center. But what protects the data center from the backup power system?
Why Diesel Is Still the Standard
Despite growing interest in natural gas and battery storage, diesel generators remain the backbone of data center backup power. Diesel starts fast — NFPA 110 classifies most data center systems as Level 1, Type 10, meaning the generator picks up load within ten seconds. Diesel is also energy-dense enough to store days of runtime in a reasonable footprint.
The fuel volumes are not small. NFPA 110 includes minimum fuel-tank capacity requirements that, for certain shorter-duration EPSS classifications, can require capacity above the calculated runtime fuel requirement. At 200 gallons per hour, 48 hours of runtime consumes 9,600 gallons before any additional tank-capacity margin. Actual required tank capacity depends on the applicable NFPA 110 classification and project requirements. Facilities with 2N redundancy store far more than that, and hyperscale campuses multiply those figures across multiple generator plants.
The Leak Detection Mistake That Keeps Getting Made
Most data centers have leak detection. Water sensing cable under the raised floor has been standard practice for years. The problem is that water-sensing cable does exactly what its name says—it detects water. Diesel fuel is non-conductive. A standard water-sensing cable will not respond to diesel contact. It will sit in a pool of fuel and report normal conditions indefinitely.
This is not a theoretical gap. A slow drip from a day tank fitting or a seeping flange on a fuel transfer line can spread along a containment tray, through a pipe trench, or under a raised floor without triggering an alarm, because the cable in its path was never designed to see it. By the time someone smells fuel or sees a sheen, the remediation is already expensive.
Hydrocarbon-specific detection cable is designed and tested to respond to specified hydrocarbon liquids rather than relying on water conductivity, meaning it alarms on diesel and fuel oil that water cable completely ignores. In a data center, where minutes of outage can mean millions in losses, that distinction is not academic.
What FM-7745 Means for Data Centers
For FM Global-insured facilities, FM Global property-loss-prevention guidance calls for FM Approved automatic leak detection in specified fuel-system locations. FM Approvals Class 7745 sets certification requirements for liquid leak detectors, including hydrocarbon detectors—testing sensitivity, response time, environmental durability, and specific liquid certification. The headline requirement: a 30-second alarm from the moment fuel contacts the sensor.
Thirty seconds matters in a data center more than almost any other building type. A diesel leak in a generator room can create a fire hazard, especially where fuel contacts hot surfaces or other ignition sources, compromises secondary containment, and begins attacking cable insulation. Faster detection reduces the time available for a leak to spread and facilitates earlier response. FM-7745 also requires that the detector be certified for the specific hydrocarbons it claims to detect — specifying "FM-7745 approved" without confirming which liquids are in the listing is one of the more common errors in data center fuel system design.
Where to Put the Sensors
Effective fuel leak detection means mapping the path from the fill point at the property line to the generator connections and covering every point where diesel can escape: bulk storage containment, day tank enclosures, sub-base tanks beneath generator sets, fuel transfer pump rooms, pipe trenches through mechanical corridors, and fill points with overflow containment.
Some of these are indoor, climate-controlled spaces. Others are outdoor pits exposed to rain, condensation, and temperature swings. The detection system must perform across all of them, and it must ignore water that collects in outdoor areas without generating false alarms that train operators to stop paying attention.
Integration with Building Management Systems
Data centers run on monitoring. A leak detection system that alarms only on a local panel depends on someone being in the right room at the right time — not reliable for a facility with minimal overnight staffing. Systems that communicate through Modbus RTU, 4–20 mA, dry contact relays, or Pt100 RTD emulation report directly into existing BMS and SCADA platforms, putting fuel alarms in the same stream as every other critical alert.
Building It In, Not Bolting It On
With data center construction moving faster than the industry has ever seen, fuel system design decisions made now will define detection capability for the next decade. For facilities where applicable code, insurer criteria, or project specifications require fuel-leak detection, incorporate hydrocarbon-specific rope sensors along fuel piping, point sensors in sumps and containment areas, and controllers that integrate cleanly with building management systems into the fuel-system design rather than treating them as an afterthought. They keep the backup power system from becoming the source of the next incident.
Naftosense builds FM-7745-approved hydrocarbon detection systems that alarm on diesel, fuel oil, and other refined fuels in under 30 seconds—with sensors that ignore water, resist false alarms, and carry a 10-year warranty. For data centers being designed or built today, the right time to spec leak detection is when you spec the generator.
To discuss the right configuration for your data center fuel system, visit www.naftosense.com or call (800) 774-5630.