40 CFR 63 Subpart ZZZZ: EPA RICE NESHAP

Regulatory citation: 40 CFR Part 63, Subpart ZZZZ, National Emission Standards for Hazardous Air Pollutants for Stationary Reciprocating Internal Combustion Engines

What Is the RICE NESHAP?

Subpart ZZZZ limits hazardous air pollutant emissions from stationary reciprocating internal combustion engines (RICE) at both major and area sources of HAP. It covers diesel and spark ignition engines used for emergency backup power, fire pumps, compressors, pumps and prime power. A major source emits or has the potential to emit 10 tons per year or more of any single HAP, or 25 tons per year or more of combined HAP. Any other source is an area source.

Requirements depend on whether the engine is new or existing, its size, its fuel, whether it is an emergency engine and whether the site is a major or area source.

Why the RICE NESHAP Matters

Backup generators and other stationary engines are found at hospitals, data centers, water plants and many other facilities. Engine exhaust contains hazardous air pollutants. Simple maintenance and limits on non-emergency running keep emissions down.

Core Requirements

1. Classify the Engine (63.6585–63.6590)

At an area source, an engine is existing if construction or reconstruction began before June 12, 2006, and new if it began on or after that date. A new or reconstructed engine at an area source meets Subpart ZZZZ by meeting the New Source Performance Standards in 40 CFR Part 60, Subpart IIII for compression ignition engines or Subpart JJJJ for spark ignition engines.

2. Follow Management Practices for Existing Area Source Engines (63.6603 and Table 2d)

For existing emergency and black start compression ignition engines at area sources, Table 2d requires changing oil and filter every 500 hours of operation or within 1 year plus 30 days, inspecting the air cleaner every 1,000 hours or within 1 year plus 30 days, and inspecting hoses and belts every 500 hours or within 1 year plus 30 days, whichever comes first, replacing parts as needed. Emergency spark ignition engines have similar oil, hose and belt intervals plus spark plug inspection every 1,000 hours or within 1 year plus 30 days.

3. Maintain Per the Manufacturer or Your Own Plan (63.6625(e))

Engines must be operated and maintained according to the manufacturer's instructions or an owner-developed maintenance plan consistent with good air pollution control practice. An optional oil analysis program under 63.6625(i) or (j) can be used to extend oil change intervals.

4. Install a Non-Resettable Hour Meter (63.6625(f))

Existing emergency engines at area sources, and existing emergency engines of 500 HP or less at major sources, must have a non-resettable hour meter installed if one is not already present.

5. Limit Startup Idling (63.6625(h))

Owners must minimize engine idle time during startup and keep startup to no more than 30 minutes, after which the normal emission standards apply.

6. Respect Emergency Engine Operating Limits (63.6640(f))

There is no time limit on running during a true emergency. Maintenance checks and readiness testing are limited to 100 hours per calendar year. Up to 50 of those hours may be used for other non-emergency situations, but not for peak shaving or to generate income, except in narrow grid reliability situations. An engine that does not follow these limits is not an emergency engine and must meet non-emergency requirements.

7. Keep Records (63.6655 and 63.6660)

Owners must keep maintenance records showing engines were maintained according to the plan, and hour meter records for emergency engines showing emergency and non-emergency hours and the reason for operation. Records must be kept for 5 years. Emergency engines over 100 HP used for certain grid reliability purposes must also file an annual report.

Common Compliance Approaches

Build an Engine Inventory

List each engine's make, model, horsepower, fuel, install date and emergency or non-emergency status.

Use a Maintenance Log With Hour Readings

Record the hour meter reading and the reason each time an engine runs, and log oil changes and inspections against the Table 2d intervals.

Schedule Testing Within Limits

Plan routine readiness tests so total non-emergency hours stay well under 100 per year.

Example: RICE NESHAP Compliance in Practice

A county water utility has an existing 400 HP diesel emergency generator at an area source pump station. The maintenance team runs a 30-minute readiness test each week and logs hour meter readings. They change oil and filter and inspect hoses and belts every 500 hours or within a year and 30 days, and inspect the air cleaner on the same annual cycle. When a storm knocks out power for two days, the operator records the hours as emergency use.

Related regulations: EPA Diesel Engine NSPS (Subpart IIII), 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

How many hours can an emergency generator run for testing?

Up to 100 hours per calendar year for maintenance checks and readiness testing. Any non-emergency operation counts toward that 100 hours. Emergency operation itself is not limited.

Does Subpart ZZZZ apply to a new generator at an area source?

Yes, but a new or reconstructed engine at an area source complies by meeting 40 CFR Part 60, Subpart IIII or JJJJ. No further requirements under Subpart ZZZZ apply to it.

Do I need an hour meter on my emergency engine?

Existing emergency engines at area sources, and those of 500 HP or less at major sources, must have a non-resettable hour meter. Under Subpart IIII, new emergency diesel engines that do not meet non-emergency standards need one before startup.