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On February 17, 2010, EPA finalized portions of the National Emission Standards for Hazardous Air Pollutants for Reciprocating Internal Combustion Engines (RICE NESHAP).  The rule was promulgated into the existing RICE standards located in 40 CFR Part 63, Subpart ZZZZ on March 3, 2010.  The newly incorporated standards were originally proposed on February 25, 2009 and apply only to stationary RICE.  The proposed standards included provisions for RICE located at area sources of hazardous air pollutants (HAPs) and RICE with a site rating of ≤ 500 brake horsepower (bhp) located at major sources of HAPs.  In addition, the proposal included standards for existing non-emergency compression ignition (CI) engines with a site rating of > 500 bhp at major sources and revised provisions related to Startup, Shutdown, and Malfunction (SSM) events for engines previously regulated under the rule.

Under the NESHAPs, a major source is defined as a site that emits > 10 tons per year (tpy) of any single HAP or > 25 tpy of combined HAPs.  An area source is a site that emits HAPs, but is not considered a major source.  A list of pollutants considered to be HAPs can be found at

Under these new regulations, many previously unregulated engines, including those designated for emergency use, are subject to federal regulation, including emission standards, control requirements, or management practices.

Following public comment on the proposed rule, EPA made a number of significant changes to the promulgated rule, including the following:

  • EPA did not finalize the proposed provisions for spark ignition (SI) engines with the exception of startup requirements.  Although the original proposal included SI engines at area sources as well as those ≤ 500 bhp located at major sources, EPA determined that additional data is needed prior to finalizing rules for these sources.  The Agency expects to finalize the rules associated with SI engines by August 10, 2010.
  • Existing emergency engines at area sources that are located at residential, commercial, or institutional facilities are not subject to the final rule.  It is important to note that a definition for a residential/ commercial/institutional facility has not been included in the final rule.
  • Several numerical standards originally proposed for some categories of engines have been replaced with management practices.
  • EPA revised the numerical emission limit for several engine categories based on a re-evaluation of the MACT floor.  The new emission limits are less stringent than those included in the proposal.
  • EPA added an option to the management practices to use an oil change analysis program to extend the oil change frequencies listed in the final rule. 
  • EPA eliminated the numerical standards originally proposed for periods of SSM,and instead promulgated operational standards that apply during startup.  Additionally, the standards that apply during normal operation now also apply during periods of shutdown and malfunction.
  • EPA included an additional requirement to reduce metallic HAP emissions for certain engine categories, including existing non-emergency CI > 300 bhp.  A closed crankcase ventilation system or open crankcase filtration system must be installed on these engines, if the engine is not already equipped with a closed crankcase ventilation system.
  • An exclusion from the numerical emission limits has been included for existing non-emergency CI RICE > 300 bhp located at area sources in Alaska that are not accessible by the Federal Aid Highway System.  These engines must meet the management practices listed for non-emergency CI RICE ≤ 300 bhp.
  • A definition for emergency stationary RICE was added in the final rule.  The majority of the requirements that apply to emergency stationary RICE listed in §63.6640(f) are identical to the proposed rule; however, the final rule allows an emergency unit to participate in an emergency demand response program as a part of a financial arrangement with another entity for up to 15 hours per year.  Additional requirements also apply to units participating in emergency demand response programs.  The detailed requirements are listed in §63.6640(f) of the final rule.

The compliance date for all applicable emission limitations and operating limitations for the affected units is three years from the effective date of the rule.  The compliance date for the sources affected by the current revision to the rule is May 3, 2013.  Following is a summary of the updated requirements for the existing stationary CI engines incorporated into the RICE NESHAP during this latest rule revision.

In addition to the requirements listed in the Updated MACT ZZZZ Requirements for Existing Stationary Reciprocating Internal Combustion Engines Table, EPA finalized startup requirements for the following stationary engines:

  • Existing CI RICE ≤ 500 hp at major sources
  • Existing non-emergency CI RICE > 500 hp at major sources
  • Existing CI RICE at area sources
  • New or reconstructed non-emergency two stroke lean burn (2SLB) < 500 hp at major sources
  • New or reconstructed non-emergency four stroke lean burn (4SLB) ≥ 250 hp at major sources
  • Existing, new, or reconstructed non-emergency four-stroke rich burn (4SRB) > 500 hp at major sources
  • New or reconstructed non-emergency CI > 500 hp at major sources

Owners and operators must minimize the engine’s startup period to the amount of time needed for appropriate and safe  loading of the engine, not to exceed 30 minutes.  After this time, the engine must meet the numerical emission standards, if applicable.

For those engines that require periodic oil changes, the schedule for changing engine oil can be extended if the oil is part of an oil analysis program.  The program must include analyzing the following parameters in order to qualify: Total Base Number, viscosity, and percent water content.  If certain limits are met during the analysis, then the owner or operator is not required to change the oil.  However, if any of the limits are exceeded, the oil must be changed prior to continuing use of the engine.  The limits are as follows:

  • Total Base Number is < 30% of the Total Base Number of the oil when new; or
  • Viscosity of the oil has changed by > 20% from the viscosity of the oil when new; or
  • Water content is > 0.5% (by volume)

In addition, recordkeeping and reporting requirements for many engines are included in the final rule.  All owners and operators of existing stationary RICE, with the exception of RICE < 100 hp, existing emergency stationary RICE, and existing stationary RICE that are not subject to numerical emission standards, must submit all applicable notifications as listed in the §63.6645 and NESHAP General Provisions (40 CFR Part 63, Subpart A).

Sources with affected RICE should review the final rule carefully to determine compliance requirements based on the promulgated standard.  For more information or to view a copy of the final rule, go to the  For assistance in determining applicability and complying with the new standards, contact your local Trinity office at (800) 229-6655.