40 CFR 60 Subpart IIII: EPA Diesel Engine NSPS

Regulatory citation: 40 CFR Part 60, Subpart IIII, Standards of Performance for Stationary Compression Ignition Internal Combustion Engines

What Is NSPS Subpart IIII?

Subpart IIII sets New Source Performance Standards for stationary compression ignition (diesel) engines, including emergency generators and fire pump engines. It applies to engine manufacturers and to owners and operators. For owners, it covers engines that commenced construction after July 11, 2005, where the engine was manufactured after April 1, 2006, or after July 1, 2006 for certified NFPA fire pump engines. It also covers engines modified or reconstructed after July 11, 2005.

For most owners, compliance means buying a certified engine, installing and maintaining it as the manufacturer directs, using the right fuel and keeping run-time records.

Why Diesel Engine Standards Matter

Diesel exhaust contains particulate matter, nitrogen oxides and other pollutants. Tier-certified engines and limits on non-emergency running reduce emissions from the many backup generators at commercial and industrial sites.

Core Requirements

1. Confirm Whether the Engine Is Covered (60.4200)

Check the construction date, manufacture date and engine type. Emergency, non-emergency and fire pump engines have different emission standards and model year tables.

2. Meet the Emission Standards (60.4205–60.4206)

Emergency engines of model year 2007 and later with a displacement under 30 liters per cylinder, other than fire pump engines, must meet the standards in 60.4202 for their model year and power rating. Engines must achieve the standards over the entire life of the engine.

3. Buy a Certified Engine (60.4211(c))

Owners of 2007 and later model year engines generally comply by purchasing an engine certified to the applicable emission standards for its model year and power.

4. Operate and Maintain Per the Manufacturer (60.4211(a))

Owners must operate and maintain the engine and any control device according to the manufacturer's emission-related written instructions, and change only settings the manufacturer permits. If the engine is not operated and maintained this way, the owner must keep a maintenance plan and records and may need a performance test within 1 year.

5. Use Compliant Diesel Fuel (60.4207)

Engines with a displacement under 30 liters per cylinder that use diesel fuel must use fuel meeting the requirements of 40 CFR 1090.305 for nonroad diesel fuel.

6. Install a Non-Resettable Hour Meter (60.4209(a))

An emergency engine that does not meet the standards for non-emergency engines must have a non-resettable hour meter installed before startup.

7. Stay Within Emergency Operating Limits (60.4211(f))

There is no time limit on use during emergencies. Maintenance checks and readiness testing are limited to 100 hours per calendar year, and up to 50 of those hours may be used for other non-emergency situations. An engine that exceeds these limits is not an emergency engine under the subpart.

8. Keep Records and File Required Reports (60.4214)

Emergency engines do not need an initial notification. Where an emergency engine does not meet non-emergency standards, the owner must record the time and reason for each run from the hour meter. Emergency engines over 100 HP used for certain grid reliability purposes must file an annual report by March 31 through EPA's CEDRI system.

Common Compliance Approaches

Keep the Certification Paperwork

File the engine's EPA certificate of conformity, nameplate photo and manufacturer manual with the site's air records.

Log Every Run

Use a simple run log with date, start and stop hour meter readings and the reason, such as weekly test or utility outage.

Specify Fuel in Purchase Orders

Require diesel fuel meeting 40 CFR 1090.305 in fuel contracts and keep delivery tickets.

Example: Subpart IIII Compliance in Practice

A distribution warehouse installs a new 750 kW certified diesel emergency generator. The facility manager keeps the certificate of conformity and the manufacturer's maintenance schedule on file. A service contractor performs maintenance as the manual requires. Monthly load tests are logged with hour meter readings, and the manager checks each quarter that non-emergency hours are on track to stay below 100 for the year.

Related regulations: EPA RICE NESHAP (Subpart ZZZZ), EPA Title V Operating Permits, EPA SPCC Rule.

Note: This summary reflects federal EPA requirements. Many state and local air agencies have delegated authority for these rules and may add their own permit conditions or stricter limits. Always check the current regulation text and any state or local rules that apply to you.

Frequently Asked Questions

Does Subpart IIII apply to my backup generator?

It applies to stationary diesel engines that commenced construction after July 11, 2005 and were manufactured after April 1, 2006, or after July 1, 2006 for certified fire pump engines, and to engines modified or reconstructed after July 11, 2005.

How many hours can I test an emergency diesel generator?

Up to 100 hours per calendar year for maintenance checks and readiness testing, including any non-emergency use. Up to 50 of those hours can be used for other non-emergency situations.

How do Subpart IIII and Subpart ZZZZ relate?

A new or reconstructed engine at an area source of HAP meets the RICE NESHAP in 40 CFR 63 Subpart ZZZZ by complying with Subpart IIII.