What NFPA 37 Means for Maintenance, Service, and Compliance

If you manage facilities, you already know emergency power isn’t just a line in your budget: it’s a life-safety and business-continuity issue.

That’s why NFPA 37 matters. This standard governs how stationary combustion engines (like your diesel or natural gas generator) are installed and used so they don’t create fire or life-safety hazards for the building and its occupants. In plain English: NFPA 37 tells you where and how your generator can live, how it must be connected and ventilated, and which protective measures need to be in place, so the unit can be maintained and serviced safely.

Below is a practical guide to what NFPA 37 covers, how it intersects with the rest of your Emergency Power Supply (EPS), the steps to stay compliant during day-to-day operation and service, and what can happen if you don’t.

Quick Overview: What NFPA 37 Covers

NFPA 37: Standard for the Installation and Use of Stationary Combustion Engines and Gas Turbines sets the minimum fire-safety requirements for engines used as prime movers for emergency generators, fire pumps, standby, and peak-shaving systems.

Think location, construction features, fuel systems, ventilation, exhaust, and fire protection around the engine and its auxiliaries. The goal is to minimize fire hazards from the unit’s installation and operation.

A few practical themes that typically affect commercial generator maintenance and service:

• • Where the generator can sit (indoor/outdoor, enclosures, proximity to openings and combustibles).
  • Fuel system details (piping, day tanks, shutoffs, protection, references to other fuel codes).
  • Air and exhaust (combustion air, room ventilation, and safe exhaust discharge).
  • Access and working clearances (for service, testing, inspections, and first-responder access).

Search terms facility teams use: “NFPA 37 generator installation requirements,” “NFPA 37 diesel generator clearance to building,” “NFPA 37 ventilation and exhaust,” “NFPA 37 vs NFPA 110.”

EPS vs. EPSS: What Part of the System Are We Talking About?

You’ll often see two acronyms in code discussions:

• • EPS (Emergency Power Supply): the generator set and its auxiliaries (the engine, alternator, radiator/heat rejection, fuel, cooling, exhaust, controls, i.e., the equipment NFPA 37 is primarily concerned with from a fire-safety standpoint).
  • EPSS (Emergency Power Supply System): the entire system from the EPS output through overcurrent devices, conductors, and transfer switches to the life-safety loads. NFPA 110 governs performance, classification (Level, Type, Class), and inspection, testing, and maintenance of the emergency and standby power system.

Put simply: NFPA 37 = safe engine installation/location. NFPA 110 = system performance and ongoing ITM. Both matter during service visits and compliance checks.

Key Areas of Your EPS Affected by NFPA 37

1. Location & Clearances
   NFPA 37 defines where engines can be installed (indoors/outdoors), how close they can be to openings (doors, windows, vents), and separation from combustible construction. A common benchmark you’ll see in manufacturer guidance and many AHJ handouts is 5 feet from wall openings and certain combustible walls (unless the listed enclosure/testing allows a different spacing). Always verify with your AHJ and the generator’s listing/manufacturer instructions.
2. Ventilation & Combustion Air
   The room or enclosure must provide adequate intake air and discharge hot air so equipment can run and be maintained safely. Poor ventilation isn’t just a performance hit; it’s a fire and service-access risk addressed by NFPA 37’s installation requirements.
3. Exhaust Systems
   Routing, shielding, and termination of exhaust must protect people and building materials and avoid recirculation into openings. Exhaust layouts are a frequent finding during service assessments because they affect both maintenance safety and code compliance.
4. Fuel Systems
   NFPA 37 coordinates with other fuel codes for tanks and piping. For example NFPA 30 (flammable/combustible liquids), NFPA 31 (oil-burning equipment), NFPA 54 (fuel gas), and NFPA 58 (LP-Gas)—so expect cross-references in your compliance checklist. Service teams often flag unprotected lines, missing shutoffs, or day-tank issues that require correction to satisfy the combined code set.
5. Access for Service & First Responders
   Engines must be readily accessible for inspection, testing, and maintenance. That means clear working space, safe approach paths, and the ability to reach protective devices and shutoffs without obstruction. This is both an NFPA 37 principle and a practical requirement manufacturers emphasize.

How to Stay Compliant During Maintenance & Service

1) Start with the right code map.
For commercial sites, you’ll typically coordinate NFPA 37 (engine installation), NFPA 110 (EPSS performance & ITM), NFPA 70/NEC (electrical), and applicable fuel codes. Align this with your local AHJ requirements (fire marshal/building department) and any applicable building or fire code editions in your jurisdiction.

2) Keep clearances clean, especially around openings and combustibles.
During service, verify the generator’s separation from doors, windows, vents, and combustible walls matches the listing/manufacturer instructions and AHJ expectations. That 5-foot rule of thumb around openings shows up in many city handouts and OEM guidance, but the listed enclosure or engineered design may allow different spacing—document what applies at your site.

3) Validate ventilation and exhaust on every visit.
Ensure intake/exhaust paths are unobstructed, louvers and dampers move freely, heat rejection is adequate, and exhaust is properly supported, insulated where needed, and terminated away from openings. These items live at the intersection of NFPA 37 and manufacturer instructions.

4) Review the fuel system against the right code(s).
Check piping protection, leak detection where required, day-tank level controls, emergency shutoffs, and separation requirements. Confirm your setup aligns with the appropriate NFPA 30/31/54/58 provisions cited by your design. Fuel issues are a common cause of AHJ corrections after service inspections.

5) Maintain NFPA 110 ITM rigor.
Even though NFPA 37 is about installation/use, your ongoing reliability and compliance posture rides on NFPA 110: periodic inspection, testing, maintenance, recordkeeping, and classification (Level/Type/Class). Keep logs tidy and ready for the AHJ.

6) Document everything and coordinate early with your AHJ.
Know who your Authority Having Jurisdiction is (fire, building, sometimes insurer) and get alignment before changes or major service actions. A quick consult can prevent costly rework.

What Happens If You’re Not Compliant?

Non-compliance is more than a checklist miss. It can lead to:

• • Fines, citations, and mandatory corrections after inspections. In serious cases, a fire marshal or AHJ can restrict operations or shut down occupancy until issues are resolved.
  • Insurance complications after an incident—ranging from premium impacts to claim disputes if code deficiencies contributed to loss.
  • Safety and downtime risks, especially if ventilation, exhaust, or fuel defects create elevated fire hazards or take the EPS out of service at the worst possible moment. (This is exactly why NFPA 110’s maintenance/testing requirements exist).

Bottom line: treating NFPA 37 (installation/use) and NFPA 110 (system performance/ITM) as a one-two program keeps you on the right side of the AHJ and protects your people, property, and uptime.

FAQs

“What’s the NFPA 37 rule on generator clearance to building?”

Most AHJs look for separation from openings/combustibles (often cited as 5 ft unless the listed enclosure/testing permits otherwise). Always confirm with your manufacturer instructions and AHJ.

“NFPA 37 vs NFPA 110—what’s the difference?”

NFPA 37 = installation/use safety for engines. NFPA 110 = performance, classification, and ongoing inspection/testing/maintenance of the EPSS. You need both.

“Does NFPA 37 apply to diesel generators?”

Yes. NFPA 37 covers stationary engines regardless of fuel; fuel tanks and piping reference other NFPA fuel codes (NFPA 30/31/54/58) that your design must also meet.

“Does NFPA 37 cover Automatic Transfer Switch (ATS) requirements?”

The requirements for the ATS itself are covered by other standards and are not specifically detailed in NFPA 37. ATS requirements come from:

• • NFPA 70 (National Electrical Code): Sets standards for the installation of electrical equipment, including the ATS.
  • NFPA 110 (Standard for Emergency and Standby Power Systems): Outlines the requirements for the performance and maintenance of the complete emergency power system, which includes the ATS.
  • UL 1008: The safety standard for transfer switches, which includes testing procedures to ensure the ATS can withstand and close on fault currents.
  • The Joint Commission (for health care): Facilities regulated by The Joint Commission have specific testing requirements for their ATS equipment.

However, NFPA 37 does affect the ATS indirectly.

As the standard for stationary engines, NFPA 37 influences the overall generator system design. The ATS must be installed in a way that aligns with these requirements.

Your Next Step: A Simple Compliance Game Plan

1. Walk the site with a NFPA 37/110 checklist (location, openings, ventilation/exhaust, fuel, access).
2. Verify listings & instructions against today’s field conditions.
3. Tighten your NFPA 110 ITM: test schedule, logs, and corrective actions.
4. Talk to your AHJ before you move equipment or modify fuel/exhaust.
5. Close the gaps with a qualified generator service partner.