The Administrator of the Environmental Protection Agency, Lisa Jackson, signed the following proposed rule on 

May 23, 2012 and we are submitting it for publication in the Federal Register. While we have taken steps to ensure 

the accuracy of this Internet version of the document, it is not the official version. Please refer to the official version 

in a forthcoming Federal Register publication, which will appear on the Government Printing Office’s FDSys 

website (http://fdsys.gpo.gov/fdsys/search/home.action) and on Regulations.gov (http://www.regulations.gov) in 

Docket No. EPA-HQ-OAR-2011-1032. Once the official version of this document is published in the Federal 

Register, this version will be removed from the Internet and replaced with a link to the official version.

6550-50-P 

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 85, 86 and 1039 

[EPA–HQ–OAR–2011–1032; FRL–9673-2] 

RIN A2060–AR46

Heavy-Duty Highway Program: Revisions for Emergency Vehicles and SCR Maintenance

AGENCY: Environmental Protection Agency (EPA) 

ACTION: Notice of Proposed Rulemaking. 

SUMMARY: This proposal consists of three parts. First, EPA is proposing revisions to its 

heavy-duty diesel regulations that would enable emergency vehicles, such as dedicated 

ambulances and fire trucks, to perform their mission-critical life-saving work without risking that 

abnormal conditions of the emission control system could lead to decreased engine power, speed 

or torque. The revisions would allow manufacturers to request and EPA to approve 

modifications to emission control systems on emergency vehicles so they do not interfere with 

the vehicles’ missions. Second, EPA is proposing to revise the emission-related maintenance 

and scheduled maintenance intervals for all motor vehicles and nonroad compression-ignition 

engines to specify minimum maintenance intervals for replenishment of consumable chemical 

reductant in connection with the use of selective catalytic reduction technologies. Third, EPA is 

proposing to offer short-term relief for nonroad engines from performance inducements related 

to the emission control system, for general purpose nonroad vehicles while operating in 

temporary emergency service. These actions are not expected to result in any significant 

changes in regulatory burdens or costs. 

DATES: Comments on all aspects of this proposal must be received on or before July 27, 2012. 

See the SUPPLEMENTARY INFORMATION section on “Public Participation” for more 

information about written comments.

Public Hearings: EPA will hold a public hearing on Wednesday, June 27, 2012 in Ann Arbor, 

Michigan. The hearing will start at 10 a.m. local time and will continue until everyone has had a 

chance to speak. For more information about the public hearing, see “How Do I Participate in 

the Public Hearing?” under the SUPPLEMENTARY INFORMATION section on “Public 

Participation” below at Section VIII.B. 

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2011-1032, 

by one of the following methods: 

• www.regulations.gov: Follow the on-line instructions for submitting comments.

• Email: a-and-r-docket@epa.gov
This document is a prepublication version, signed by the Administrator of the Environmental Protection Agency, 

Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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• Fax: (202) 566-9744 

• Mail: Environmental Protection Agency, Air Docket, Mail-code 6102T, 1200 Pennsylvania 

Ave., NW, Washington, DC 20460. 

• Hand Delivery: EPA Docket Center (EPA/DC), EPA West, Room 3334, 1301 Constitution 

Ave., NW., Washington, DC, Attention Docket No. EPA-HQ-OAR-2011-1032. Such 

deliveries are only accepted during the Docket’s normal hours of operation, and special 

arrangements should be made for deliveries of boxed information. 

Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-2011-1032. For 

additional instructions on submitting written comments, see the SUPPLEMENTARY 

INFORMATION section on “Public Participation” below at Section VIII.A. 

Docket: All documents in the docket are listed in the www.regulations.gov index. Although 

listed in the index, some information is not publicly available, e.g., confidential business 

information or other information whose disclosure is restricted by statute. Certain other material, 

such as copyrighted material, will be publicly available only in hard copy in the docket. Publicly 

available docket materials are available either electronically in www.regulations.gov or in hard 

copy at the EPA Docket Center, EPA/DC, EPA West, Room 3334, 1301 Constitution Ave., NW, 

Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday 

through Friday, excluding legal holidays. The telephone number for the Public Reading Room is 

(202) 566-1744, and the telephone number for the Air Docket is (202) 566-1742. 

FOR FURTHER INFORMATION CONTACT: Lauren Steele, Environmental Protection 

Agency, Office of Transportation and Air Quality, Assessment and Standards Division, 2000 

Traverwood Drive, Ann Arbor, Michigan 48105; telephone number: 734-214-4788; fax number: 

734-214-4816; email address: steele.lauren (@epa.gov). 

SUPPLEMENTARY INFORMATION: 

Does this action apply to me?

This proposed action would affect you if you produce or import new heavy-duty or nonroad 

diesel engines that are intended for use in vehicles that serve the emergency response industry, 

including all types of dedicated and purpose-built fire trucks and ambulances. You may also be 

affected by this action if you manufacture diesel engines that make use of a consumable 

chemical reductant to comply with emissions standards for nitrogen oxides. You may also be 

affected by this action if you produce or import diesel engines for nonroad applications. The 

following table gives some examples of entities that may be affected by this proposed action. 

Because these are only examples, you should carefully examine the proposed and existing 

regulations in 40 CFR parts 85, 86 and 1039. If you have questions regarding how or whether 

these rules apply to you, you may call the person listed in the FOR FURTHER 

INFORMATION CONTACT section above. 
This document is a prepublication version, signed by the Administrator of the Environmental Protection Agency, 

Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

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Category NAICS Codesa Examples of Potentially Regulated Entities

Industry 336111

336112 

333618 

336120

Engine and Truck Manufacturers

Industry 541514

811112 

811198

Commercial Importers of Vehicles and Vehicle 

Components 

Industry 811310 Engine Repair, Remanufacture, and Maintenance

Note:

a North American Industry Classification System (NAICS)

Table of Contents 

I. Overview

A. Emergency Vehicle Provisions

B. Diesel Exhaust Fluid Provisions

C. Nonroad Equipment Used Temporarily in Emergency Service

II. Statutory Authority and Regulatory Background

A. Statutory Authority

B. Background: 2007 and 2010 NOX and PM Standards

(1) On-Highway Standards

(2) Nonroad Standards

III. Direct Final Rule

IV. Emergency Vehicle Provisions

A. Background on Regulation of Emergency Vehicles

B. Current Provisions for Other Emergency Vehicles and Engines

C. Why is EPA Taking This Action?

(1) How Does a DPF Work?

(2) Why Are Emergency Vehicles Having Problems with DPF Regeneration?

(3) What Are the Concerns for Emergency Vehicles Using SCR?

D. What Would Occur if EPA Took No Action?

(1) The Industry Would Continue to Get Smarter

(2) The Fleet Would Continue to Migrate to the 2010 Standards

(3) Some Trucks Would Continue to Experience Problems

E. Proposed Regulatory Action

(1) Liberalized Regeneration Requests

(2) Engine Recalibration

(3) Backpressure Relief
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version.

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F. What Engines and Vehicles Would be Affected?

(1) Newly Certified Engines and Vehicles

(2) Certified Engines and Vehicles In-Use

(3) Labeling Requirements

(4) Other Regulatory Provisions

V. Scheduled Maintenance and Maintenance Interval for Replacement of Diesel Exhaust Fluid

A. Background

B. Proposed Regulatory Action

(1) Scheduled Emission-Related Maintenance

(2) Maintenance Intervals for On-Highway Diesel Engines

(3) Maintenance Intervals for Nonroad Compression-Ignition Engines

VI. Nonroad Engines in Temporary Emergency Service

A. Use of Nonroad Engines in Emergency Situations

B. Proposed Regulatory Action

(1) General Requirements

(2) Approval Criteria

(3) Allowable Use of Emergency AECD’s

VII. Economic, Environmental, and Health Impacts of Proposed Rule

A. Economic Impacts

(1) Economic Impacts of Emergency Vehicle Proposal

(2) Economic impacts of SCR Maintenance Proposal

(3) Economic Impacts for Nonroad Engines Used in Emergency Situations

B. Environmental Impacts

(1) Environmental Impacts of Emergency Vehicle Proposal

(2) Environmental Impacts of SCR Maintenance Proposal

(3) Environmental Impacts for Nonroad Engines Used in Emergency Situations

C. Health Effects

VIII. Public Participation

A. How Do I Submit Comments?

B. Will There Be a Public Hearing?

IX. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive Order 13563: 

Improving Regulation and Regulatory Review

B. Paperwork Reduction Act

C. Regulatory Flexibility Act

D. Unfunded Mandates Reform Act

E. Executive Order 13132: Federalism
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F. Executive Order 13175: Consultation and Coordination with Indian Tribal Governments

G. Executive Order 13045: Protection of Children from Environmental Health and Safety Risks

H. Executive Order 13211: Energy Effects

I. National Technology Transfer Advancement Act

J. Executive Order 12898: Federal Actions to Address Environmental Justice in Minority 

Populations and Low-Income Populations

I. Overview 

A. Emergency Vehicle Provisions

EPA is proposing amendments to its heavy-duty diesel engine programs that would 

specifically allow engine manufacturers to request to deploy specific emission controls or 

settings for new and in-use engines that are sold for use only in emergency vehicles. EPA is 

proposing these revisions to enable fire trucks and ambulances with heavy-duty diesel engines to 

perform mission-critical life- and property-saving work without risk of losing power, speed or 

torque due to abnormal conditions of the emission control systems. 

EPA’s current diesel engine requirements have spurred application of emission controls 

systems such as diesel particulate filters (commonly called soot filters or DPF’s) and other aftertreatment systems on most new diesel vehicles, including emergency vehicles. Some control 

system designs and implementation strategies are more effective in other segments of the fleet 

than in emergency vehicles, especially given some emergency vehicles’ extreme duty cycles. By 

this action, EPA intends to help our nation’s emergency vehicles perform their missions; to 

better ensure public safety and welfare and the protection of lives and property. 

B. Diesel Exhaust Fluid Provisions

EPA is proposing to amend its regulations for diesel engines to add provisions specifying 

emission-related maintenance and scheduled maintenance intervals for replenishment of 

consumable chemical reductant in connection with engines and vehicles that use selective 

catalytic reduction (SCR) technologies. This would apply to the use of SCR with model year 

(MY) 2011 and later light-duty vehicles and nonroad compression ignition (NRCI) engines, and 

MY 2012 and later heavy-duty vehicles and engines. 

Most manufacturers of diesel engines and vehicles subject to our current standards 

regulating oxides of nitrogen (NOX) have chosen to use a NOX reduction technology known as 

selective catalytic reduction (SCR) in order to meet these requirements. SCR systems use a 

chemical reductant that usually contains urea and is known as diesel exhaust fluid (DEF). The 

DEF is injected into the exhaust gas and requires periodic replenishment by refilling the DEF 

tank. 

Given that SCR use is now common in the transportation sector and replenishment of 

DEF is necessary for SCR to be effective, it is appropriate to add DEF replenishment to the list 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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of scheduled emission-related maintenance published in the Code of Federal Regulations (CFR), 

rather than rely on a case-by-case approval as is specified in the current regulations. This action 

would improve the clarity and transparency of EPA’s requirements for SCR systems. 

C. Nonroad Equipment Used Temporarily in Emergency Service

EPA is proposing short-term relief from emission control system performance 

inducements for any nonroad compression ignition engine powered vehicles operating in 

temporary emergency service. This relief would address concerns about unusual circumstances 

where performance inducements could hinder equipment performance in emergency conditions, 

which are defined as conditions in which the functioning (or malfunctioning) of emission 

controls poses a significant risk to human life. We are proposing provisions for a short-term 

emergency bypass of the normal emission controls, including inducement strategies, which could 

result in a loss of power of an engine; thus, allowing the equipment to temporarily perform 

emergency-related work. By this action, EPA would help our nation’s nonroad equipment 

perform temporary emergency service; to better ensure public safety and welfare and the 

protection of lives. 

II. Statutory Authority and Regulatory Background

A. Statutory Authority

Section 202(a)(1) of the Clean Air Act (CAA or the Act) directs EPA to establish 

standards regulating the emission of any air pollutant from any class or classes of new motor 

vehicles or new motor vehicle engines that, in the Administrator’s judgment, causes or 

contributes to air pollution which may reasonably be anticipated to endanger public health or 

welfare. Such standards apply for the useful life of the vehicles or engines. Section 202(a)(3) 

requires that EPA set standards applicable to emissions of hydrocarbons, carbon monoxide, NOX

and particulate matter (PM) from heavy-duty trucks that reflect the greatest degree of emission 

reduction achievable through the application of technology which we determine will be available 

for the model year to which the standards apply. We are to give appropriate consideration to 

cost, energy, and safety factors associated with the application of such technology. We may 

revise such technology-based standards, taking costs into account, on the basis of information 

concerning the effects of air pollution from heavy-duty vehicles or engines and other sources of 

mobile source related pollutants on the public health and welfare. 

Section 202(a)(4)(A) of the Act requires the Administrator to consider risks to public 

health, welfare or safety in determining whether an emission control device, system or element 

of design shall be used in a new motor vehicle or new motor vehicle engine. Under section 

202(a)(4)(B), the Administrator shall consider available methods for reducing risk to public 

health, welfare or safety associated with use of such device, system or element of design, as well 

as the availability of other devices, systems or elements of design which may be used to conform 

to requirements prescribed by (this subchapter) without causing or contributing to such 

unreasonable risk. 
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Section 206(a) of the Act requires EPA to test, or require to be tested in such manner as it 

deems appropriate, motor vehicles or motor vehicle engines submitted by a manufacturer to 

determine whether such vehicle or engine conforms to the regulations promulgated under section 

202. Section 206(d) provides that EPA shall by regulation establish methods and procedures for 

making tests under section 206. 

Section 213 of the Act gives EPA the authority to establish emissions standards for 

nonroad engines and vehicles (42 U.S.C. 7547). Sections 213(a)(3) and (a)(4) authorize the 

Administrator to set standards and require EPA to give appropriate consideration to cost, lead 

time, noise, energy, and safety factors associated with the application of technology. Section 

213(a)(4) authorizes the Administrator to establish standards to control emissions of pollutants 

(other than those covered by section 213(a)(3)) which “may reasonably be anticipated to 

endanger public health and welfare.” Section 213(d) requires the standards under section 213 to 

be subject to sections 206-209 of the Act and to be enforced in the same manner as standards 

prescribed under section 202 of the Act. 

B. Background: 2007 and 2010 NOX and PM Standards

(1) On-Highway Standards

On January 18, 2001, EPA published a rule promulgating more stringent standards for 

NOX and PM for heavy-duty highway engines (“the heavy-duty highway rule”).1 The 0.20 gram 

per brake-horsepower-hour (g/bhp-hr) NOX standard in the heavy-duty highway rule first applied 

in MY 2007. However, because of phase-in flexibility provisions adopted in that rule and use of 

emission credits generated by manufacturers for early compliance, manufacturers were able to 

continue to produce engines with NOX emissions greater than 0.20 g/bhp-hr. The phase-in 

provisions ended after MY 2009 so that the 0.20 g/bhp-hr NOX standard was fully phased-in for 

model year 2010. Because of these changes that occurred in MY 2010, the 0.20 g/bhp-hr NOX

emission standard is often referred to as the 2010 NOX emission standard, even though it applied 

to engines as early as MY 2007. 

The heavy-duty highway rule adopted in 2001 also included a PM emissions standard for 

new heavy-duty diesel engines of 0.01 g/bhp-hr, effective for engines beginning with MY 2007. 

Due to the flexible nature of the phase-in schedule described above, manufacturers have had the 

opportunity to produce engines that met the PM standard while emitting higher levels of NOX. 

During the phase-in years, manufacturers of diesel engines generally produced engines that were 

tuned so the combustion process inherently emitted lower engine-out NOX while relying on PM 

after-treatment to meet the PM standard. The principles of combustion chemistry dictate that

conditions yielding lower engine-out NOX emissions generally result in higher engine-out PM 

emissions. This is what we call the NOX-PM trade-off. For many new low-NOX diesel engines 

today, engine-out PM emissions could be at or above the levels seen with the MY 2004 standards 

 

1 Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine and Vehicle Standards and Highway 

Diesel Fuel Sulfur Control Requirements (66 FR 5001).
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

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(0.1 g/bhp-hr). To meet today’s stringent PM standards, manufacturers rely on diesel particulate 

filter after-treatment to clean the exhaust. 

(2) Nonroad Standards

EPA adopted similar technology-forcing standards for nonroad diesel engines on June 29, 

2004.2

 These are known as the Tier 4 standards. This program includes requirements that will 

generally involve the use of NOX after-treatment for engines above 75 hp and PM after-treatment 

(likely soot filters) for engines above 25 hp. These standards phase in during the 2011 to 2015 

time frame.

III. Direct Final Rule

In addition to this notice of proposed rulemaking, EPA is also publishing a Direct Final 

Rule (DFR) addressing the emergency vehicle provisions described in Section IV of this 

document. We are doing this to expedite the regulatory process to allow engine and vehicle 

modifications to occur as soon as possible. However, if we receive relevant adverse comment on 

distinct elements of the emergency vehicle provisions in this proposal by July 27, 2012, we will 

publish a timely withdrawal in the Federal Register indicating which provisions we are 

withdrawing. Any provisions of the DFR that are not withdrawn will become effective on 

[Insert date 60 days from date of publication in the Federal Register], notwithstanding 

adverse comment on any other provision. We will address all public comments in the final rule 

based on this proposed rule.

As noted above, EPA is publishing the DFR to expedite the deployment of solutions that 

will best ensure the readiness of the nation’s emergency vehicles. We request that commenters 

identify in your comments any portions of the emergency vehicle proposed action described in 

Section IV below with which you agree and support as proposed, in addition to any comments 

regarding suggestions for improvement or provisions with which you disagree. In the case of a 

comment that is otherwise unclear whether it is adverse, EPA would interpret relevant comments 

calling for more flexibility or less restrictions for emergency vehicles as supportive of the direct 

final rule. In this way, the EPA will be able to adopt those elements of the DFR that are fully

supported and most needed today, while considering and addressing any adverse comments 

received on the proposed rule, in the course of developing the final rule. 

Note that Docket Number EPA-HQ-OAR-2011-1032 is being used for both the DFR and 

this Notice of Proposed Rulemaking (NPRM). 

 

2 Control of Emissions of Air Pollution from Nonroad Diesel Engines and Fuel (69 FR 38958).
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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IV. Emergency Vehicle Provisions

A. Background on Regulation of Emergency Vehicles

Typically, the engines powering our nation’s emergency vehicles belong to the same 

certified engine families as engines that are installed in similarly sized vehicles sold for other 

public and private uses.3

 Historically, engine and vehicle manufacturers have sought EPA 

certification for broad engine families and vehicle test groups that are defined by similar 

emissions and performance characteristics. Engine families typically only consider the type of 

vehicle in which the engine is intended to be installed to the extent that it fits into a broad vehicle 

weight class and, to a lesser extent, the vehicle’s intended duty cycle (i.e. urban or highway). 

Because of the above-described manufacturing practices and the narrow CAA authority 

for any exemptions, EPA has historically regulated engines for emergency vehicles, including 

ambulances as well as police vehicles and fire-fighting apparatus, in the same manner as other 

engines. 

In the public comments received on the proposed heavy-duty highway rule, EPA received 

some comments about DPF technologies and regeneration cycles on heavy-duty trucks, including 

one comment that expressed concerns that the systems may not be failsafe.

4

 However, none of 

the comments specifically raised technical feasibility with respect to emergency vehicles, and 

EPA’s response was based on the best information available at the time. After publishing the 

final rule requiring heavy-duty highway engines to meet performance standards that compelled 

technologies such as DPF’s, EPA received a letter from the National Association of State Fire 

Marshals, requesting some provision for public safety in implementing this new rule, considering 

that fire departments across the nation have trouble covering basic costs and may not have funds 

for more expensive trucks.5 This letter did not raise any technical feasibility issues, and EPA did 

not see a need to take action. 

More recently EPA has received letters from fire apparatus manufacturers and ambulance 

companies requesting relief from power or speed inducements related to low levels of DEF for 

SCR systems on emergency vehicles.

6

 Power and speed reduction inducements were new on 

vehicles equipped with SCR. These were not specifically mandated by EPA but designed by 

manufacturers to occur if DEF levels became low, to induce operators of the vehicles to perform 

 

3 In this proposal, emergency vehicle is defined as a fire truck or an ambulance for on-highway applications, and for 

nonroad applications, we are defining emergency equipment as specialized vehicles to perform aircraft rescue and 

firefighting functions at airports, or wildland fire apparatus. See Section IV.C and proposed revisions at 40 CFR 

86.1803-01 and 40 CFR 1039.801. 4 Heavy-Duty Highway Final Rule, December 21, 2000 Response to Comments, Section 3.2.1, “Technical 

Feasibility of Engine/Vehicle Standards//Diesel Engine Exhaust Standards,” page 3-58 to 3-60, available at 

http://www.epa.gov/otaq/highway-diesel/regs/2007-heavy-duty-highway.htm. 5 Letter dated February 1, 2001 to C. Whitman, EPA Administrator from G. Miller, President, National Association 

of State Fire Marshalls

6 See, for example, letter dated October 22, 2009, from Roger Lackore of the Fire Apparatus Manufacturers’ 

Association and Randy Hanson of the Ambulance Manufacturers Division, to Keisha Jennings of EPA.
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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the required emission-related maintenance in use. More discussion on this, including why the 

emergency response community requested relief and what action EPA took, is found below in 

Section IV.C(3). 

Recently, beginning in October 2011, EPA received a series of comment letters from fire 

chiefs and other interested stakeholders, requesting regulatory action to relieve emergency 

vehicles from the burden of complying with the 2007 PM standards.7

 EPA promptly opened a 

dialogue with the fire chiefs and engine manufacturers to understand the issues. Power and speed 

reductions were occurring on some vehicles with soot filters but without SCR systems, in part 

related to engine protection measures designed by manufacturers. Essentially, these soot filters 

are supposed to be self-cleaning by periodically burning off accumulated soot during normal 

vehicle use. The cleaning process is called regeneration, and when this doesn’t work as 

designed, the filter gradually gets more clogged, which can lead to engine problems. EPA has 

determined that while other pathways are available for resolving some issues related to soot 

filters on emergency vehicles, there remains a public safety issue related to design of engines and 

emission control systems on emergency vehicles that should be addressed through this 

rulemaking. More discussion of this, including why relief was requested and what other actions 

can be taken in addition to EPA regulation, is found below in Sections IV.C and IV.D. 

B. Current Provisions for Other Emergency Vehicles and Engines

On December 1, 2011, in a proposed rule issued jointly with the National Highway 

Traffic Safety Administration (NHTSA), EPA proposed to exclude light-duty emergency and 

police vehicles from all phases of greenhouse gas (GHG) emissions standards, in part due to 

concerns related to technical feasibility, and in part to harmonize with NHTSA’s program. 

Consistent with authority under the Energy Policy and Conservation Act, NHTSA’s corporate 

average fuel economy program already provides manufacturers with the option to exclude 

emergency vehicles.8

 The agencies are considering and responding to comments on this 

proposal, and plan to finalize this rule in summer 2012. 

In addition to the above proposed exemption for on-highway engines from GHG 

standards, EPA has provided limited regulatory relief for other types of emergency-use engines. 

First, EPA’s May 6, 2008 final rule adopting Tier 3 and Tier 4 standards for marine diesel 

engines allows for emergency and rescue vessels to meet an earlier, less stringent tier of 

standards under 40 CFR parts 89, 94 and 1042.9

 We adopted these provisions to avoid 

compromising engine performance during emergency operation, and to ensure that more 

stringent emission standards did not cause a situation where there were no certified engines 

available for emergency vessels. Such engines are not subject to the Tier 4 standards, which 

 

7 See, for example, letter dated October 4, 2011 from Congressman Filner to EPA Administrator Jackson, and letter 

dated October 14, 2011, from Director Cimini of the Southeast Association of Fire Chiefs to EPA Administrator 

Jackson.

8 See 49 U.S.C. 32902(e). 9 Final Rule: Control of Emissions of Air Pollution from Locomotives and Marine Compression-Ignition Engines 

Less Than 30 Liters per Cylinder, 73 FR 25098, May 6, 2008, and republished to correct typographical errors on 

June 30, 2008, 73 FR 37096.
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generally involve selective catalytic reduction and diesel particulate filters. The regulations also 

allow for meeting less stringent standard if there are no suitable engines that are certified to the 

current standards. 

EPA also adopted limited exemption provisions for emergency rescue equipment for 

small spark-ignition nonroad engines in 1999.10 Under this provision, equipment manufacturers 

needed to demonstrate that no engine models certified to current emission standards were 

available to power the emergency rescue equipment. We recently moved this provision to 40 

CFR part 1054 and included a variety of elements to clarify and improve oversight of the 

exemption in a later final rule.11 These elements include a requirement that the engines meet the 

most stringent standards feasible (but less than the current standards for certification) and annual 

reporting to EPA on the availability of compliant engines that meet the needs of other emergency 

equipment using such engines. 

In these rules, EPA recognized that equipment and vessels designed and purpose-built 

exclusively for use in emergency equipment have demanding performance specifications and in 

some cases extreme duty cycles. The marine diesel provisions also recognize that engines 

certified to the latest emissions standards requiring emissions after-treatment may create some 

interference with engine performance or effectiveness that may be needed in emergency 

circumstances, when installed in some emergency equipment or vessels. 

While these provisions do offer limited relief from the latest round of emissions standards 

for these engines, there is a general requirement to use engines meeting the most stringent 

emission standards as practical. There are also additional administrative responsibilities related 

to engine labeling, periodic reporting to EPA, and recordkeeping. These provisions in some 

cases also expire if compliant engines become available that can practically be used to provide 

power for the equipment in question. Furthermore, these limited exemption provisions are only 

applicable to newly certified engines. The regulations do not apply these provisions to in-use 

engines that are certified and deployed in emergency equipment.

C. Why is EPA Taking This Action?

EPA is proposing to amend its regulations to facilitate engine manufacturers’ design and

implementation of reliable and robust emission control systems with regeneration strategies and 

other features that do not interfere with the mission of emergency vehicles. Through the 

comments and letters we have received, as well as our own outreach and data-gathering efforts, 

we have learned that some emission control systems on fire trucks and ambulances today, in 

particular, certain applications using diesel particulate filters, are requiring an unexpected

amount of operator interventions, and there are currently a nontrivial number of emergency 

vehicles that are electronically programmed to cut power or speed – even while responding to an 

 

10 Final Rule: Phase 2 Emission Standards for New Nonroad Spark-Ignition Nonhandheld Engines at or Below 19 

Kilowatts, 64 FR 15208, March 30, 1999. 11 Final Rule: Control of Emissions from Nonroad Spark-Ignition Engines and Equipment, 73 FR 59034, October 8, 

2008.
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emergency - when certain operational parameters are exceeded in relation to the emission control 

system. As we understand it, the experiences of operators are mixed, with some not reporting 

any problems and some reporting problems that raise public safety and welfare concerns. 

EPA’s standards are performance-based, and reflect the greatest degree of emission 

reduction achievable, according to CAA sections 202(a)(3) and 213(a)(3). Our on-highway and 

nonroad PM standards do not specify the type of diesel particulate filter for manufacturers to use, 

nor do they even mandate the use of such a filter. Our analysis of the feasibility of the 2007 onhighway PM standard is presented in Chapter III of the final Regulatory Impact Analysis (RIA)

for that rule.

12 Our analysis of the feasibility of the Tier 4 nonroad compression ignition engine 

standards that will be phasing in through 2015 is presented in Chapter 4 of that rule’s final 

RIA.13 For most nonroad engines, these standards are similar in stringency to the 2007 onhighway heavy-duty engine and vehicle standards. As described below in Section VII, these two

rules are providing billions of dollars of annual health benefits by virtually eliminating harmful 

PM emissions from the regulated engines. Even so, EPA is required by sections 202(a)(4)(B) 

and 213(c) of the Act to, among other things, consider methods for reducing risk to public safety 

and welfare associated with the use of emission control devices or systems. 

Based on the information available to us, we have concluded that there is an indirect risk 

to public safety and welfare associated with some examples of emission control systems when 

they are deployed on emergency vehicles that experience extreme duty cycles. This indirect risk 

is related to the readiness of emergency vehicles and the risk that they may not be able to 

respond during emergencies with the full power, torque, or speed that the engine is designed to 

provide. While this risk is not inherent to the requirement to reduce emissions or to the use of 

diesel particulate filters on emergency vehicles, EPA believes it is appropriate to ensure that 

emergency vehicles can perform their emergency missions without the chance of such 

consequences. 

EPA’s current rules already provide the opportunity for manufacturers to address many 

issues through applications for certification of new engines and new vehicles. There is also 

currently a mechanism for manufacturers to deploy field modifications to the in-use fleet, 

including those that are substantially similar to approved upgrades for new vehicles, as well as 

those that apply only to vehicles that are no longer in production. As manufacturers become 

aware of the need for upgrades or enhancements, this process occurs within the new and in-use 

fleet with various degrees of application. While that process is occurring today, EPA views this

issue as serious enough that we would be remiss if we did not act to ensure that our regulations 

clearly offer the needed flexibilities for emergency vehicles. 

 

12 Final Regulatory Impact Analysis for the “2007 Heavy-Duty Highway Rule,” EPA420-R-00-026, December 

2000. Chapter III, Emissions Standards Feasibility, is available at http://www.epa.gov/otaq/highway-diesel/regs/riaiii.pdf

13 Final Regulatory Impact Analysis for “Control of Emissions from Nonroad Diesel Engines,” EPA420-R-04-007, 

May 2004. Chapter 4, Technologies and Test Procedures for Low-Emission Engines, is available 

http://www.epa.gov/nonroad-diesel/2004fr/420r04007e.pdf
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(1) How Does a DPF Work? 

To explain more fully the issues that we are addressing with this action, and hence why 

we are taking this action, we are providing here some background information on diesel 

particulate filters and the process of DPF regeneration. DPF’s are exhaust after-treatment 

devices that significantly reduce emissions from diesel-fueled vehicles and equipment. DPF’s

physically trap PM and remove it from the exhaust stream. Figure IV-1 depicts a schematic of a 

wall-flow monolith style filter, with the black arrows indicating exhaust gas laden with particles, 

and the gray arrows indicating filtered exhaust gas. This style of filter is the most common in 

today’s heavy-duty diesel engines, and has very high rates of filtration, in excess of 95 percent.14 

Figure IV-1 Illustration of air flow pattern in a wall-flow monolith style PM filter (Source: Corning)

To be successful, these devices generally must be able to accomplish two things: collect 

PM and clean away accumulated PM. There are two main types of PM that can accumulate: 

combustible and non-combustible, and two very different types of cleaning methods: 

regeneration and ash cleaning. Regeneration occurs relatively frequently, and is designed to 

complete the combustion (oxidation) of the trapped combustible PM components, releasing them 

to the exhaust as gas-phase compounds (mostly H2O and CO2). In contrast to the PM that can be 

oxidized and carried out the tailpipe as gases, the non-combustible PM such as metallic ash

cannot be destroyed through regeneration and will always remain inside a DPF. To clean ash 

from a DPF, the filter unit is removed from the vehicle and professionally cleaned with a special 

machine. Fortunately, there is very little ash formation from modern diesels so ash cleaning and 

ash disposal occurs very infrequently, generally with at least 150,000 mile service intervals, and 

 

14 See Final RIA Chapter III, Note 12, above.
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the mass of accumulated ash is generally small (a few teaspoons).15,16 This distinction is made 

here because the ash cleaning process is not a source of concern that has given rise to this EPA 

action. The infrequent cleaning of noncombustible materials from DPF’s is not part of the scope 

of this action. 

 Regeneration, however, is a type of routine DPF cleaning that must occur regularly, and 

for which EPA does not specify a minimum interval in its regulations, in contrast to the ash 

cleaning process. At its very essence, regeneration involves burning off the accumulated soot. 

Since this burning can involve extra heat and/or oxygen or oxygen-containing compounds, this 

must be done carefully and safely to avoid uncontrolled burns. The discussion below in Section 

IV.C.(1)(b) describes the three types of routine DPF regeneration: passive regeneration, 

automatic active regeneration, and manual (parked) active regeneration. A more detailed 

discussion is provided in a memorandum to the docket.17 Before discussing the ways that 

manufacturers achieve regeneration, though, first we discuss the reason why it is needed at all. 

(a) Failure of a DPF 

When the style of filter installed on a diesel vehicle is the wall-flow type that is 

predominant in the market today, it physically traps so much of the PM that the particles 

accumulate on the inside of the filter and if not burned off, this PM can over time block the 

passages through the filtering media, making it more restrictive to exhaust flow. This is

commonly referred to as “trap plugging.” Some other styles of filter, such as flow-through 

DPF’s, are less prone to plugging, but do not generally reduce the PM emission rate sufficiently 

to meet today’s stringent PM standard. Any time something gets in the way of free flowing air 

through an engine, it creates what we call “exhaust backpressure.” Even a clean, new DPF 

generates a small amount of exhaust backpressure due to the porous walls through which all of 

the exhaust flows. 

Engines can tolerate a certain range of exhaust backpressure. When an increase in this 

backpressure, or resistance, is detected, engines can compensate to a point. An increase in

exhaust backpressure from a DPF trapping more and more PM represents increased work 

demanded from the engine to force the exhaust gas through the increasingly restrictive DPF. 

However, unless the DPF is frequently cleansed of the trapped PM, this increased work demand

can lead to reductions in engine performance and increases in fuel consumption. This loss in 

performance may be noticed by the vehicle operator in terms of poor acceleration and generally 

poor drivability of the vehicle. 

If a DPF is not regenerated and it becomes plugged, there is a risk of two types of failure. 

The degree of this risk and which consequence may be experienced will depend on the engine 

and emission control system design. One consequence is that the lack of air flowing through an 

 

15 EPA’s regulations at 40 CFR 86.004-25(b)(4) for heavy-duty diesel engine maintenance specify a minimum 

interval for DPF ash cleanout from 100,000 to 150,000 mi. Many manufacturers design DPF systems with longer 

maintenance intervals.

16 See http://www.arb.ca.gov/diesel/tru/documents/ashguide.pdf 17 See memo dated May 4, 2012, “Diesel Particulate Filter Regeneration,” Docket ID EPA-HQ-OAR-2011-1032. 
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version.

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engine will cause an engine to shut down because it can no longer compensate for the extra work 

being demanded of it. The other is a risk of catastrophic DPF failure when excessive amounts of 

trapped PM begin to oxidize at high temperatures (i.e., DPF regeneration temperatures above 

1,000°C) leading to a “runaway” combustion of the PM within the DPF. This can cause 

temperatures in the filter media to increase beyond its physical tolerance, possibly creating high 

thermal stresses where the DPF materials could crack or melt. This is an unsafe condition, 

presenting physical danger to occupants as well as to objects and persons near the vehicle. 

Further, catastrophic failure can allow significant amounts of the diesel PM to pass through the 

DPF without being captured. That is, the DPF is destroyed and PM emission control is lost. For 

all these reasons, most manufacturers generally design their emission control systems to prevent 

uncontrolled shutdown or runaway DPF regeneration by programming the engine’s electronic 

control module (ECM) to limit maximum engine speed, torque and/or power when excessive 

backpressures are detected. This mode of engine operation at reduced performance may allow a 

vehicle to “limp home” to receive service. In extreme cases the ECM may command the engine 

to shut down to prevent a catastrophic failure.

(b) Types of Regeneration 

There are three types of routine DPF regeneration. Passive regeneration refers to methods 

that rely strictly on the temperatures and constituents normally available in the vehicle’s exhaust 

to oxidize PM from a DPF in a given vehicle application. Passive regeneration is an automatic 

process that occurs without the intervention of an engine’s on-board diagnostic and control 

systems, and often without any operator notice or knowledge. Passive regeneration is often a 

continuous process, because of which, it is sometimes referred to as continuous regeneration. In 

a vehicle whose normal operation does not generate temperatures needed for passive DPF 

regeneration, the system needs a little help to clean itself. This process is called active 

regeneration, and supplemental heat inputs to the exhaust are provided to initiate soot oxidation. 

There are two types of active regeneration: those that may occur automatically either while the 

vehicle is in motion, while idling, or while powering an auxiliary device such as a pump or 

ladder (power take-off (PTO) mode)), and those that must be driver-initiated and occur only 

while the vehicle is stationary and out-of-service. 

Vehicles with automatic active regeneration systems require operators to be alert to 

dashboard lamps and indicators. Written instructions are provided to operators to explain what 

each lamp means (such as high temperatures or need for regeneration) and what action is called 

for (such as driving at highway speeds or initiating a manual active regeneration). Because EPA 

emissions standards are performance based; and therefore, do not dictate any required emission 

control system technologies or configurations, each manufacturer has the discretion to program 

the timing and sequence of lamps as needed to inform drivers of the condition of the emission 

control system. As noted above, it is not uncommon in today’s heavy-duty fleet for an engine’s 

ECM to limit its maximum speed, torque or power when a plugging DPF is detected. These 

engine and emission control system protection measures can alert drivers to the need to change 

driving conditions to facilitate automatic active regeneration or to make plans to allow for a 

manual active regeneration. 
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A manual active regeneration allows the engine’s ECM to increase engine speed and 

exhaust temperature to a greater extent than what is typically allowed during an automatic active 

regeneration. Because the ECM takes full control of an engine during a manual active 

regeneration, the vehicle must remain parked and not used for other purposes, such as pumping 

water in PTO mode. Some manual active regenerations may require towing the vehicle to a 

special service center, and may occur while the DPF is on the vehicle, or offline with the DPF 

removed from the vehicle. In such cases, if a spare DPF is not available, the vehicle could be out 

of service overnight. If a driver disregards such warnings, the risk of uncontrolled engine 

shutdown or a catastrophic DPF failure may increase. EPA encourages the design of robust 

systems calling for minimal driver interventions, while providing drivers with clear and early 

indicators before any interventions are needed. EPA also encourages accurate and thorough 

operator training to ensure that the correct remedial action is taken at the earliest available time.

Actively regenerating DPF systems typically require sufficient air flow, temperature and 

soot accumulation before an automatic active regeneration will be requested by the engine’s 

ECM. As mentioned above, this may occur either while the vehicle is in motion or parked, if 

pre-set engine operating conditions are met (such as speed and temperature). When the engine’s 

ECM signals the initiation of an automatic active regeneration and the extra heat is generated, an 

ideal DPF system accomplishes this as a transparent process, with no effects perceivable by the 

driver.

A variety of manufacturer approaches can be taken to produce the supplemental heat 

needed for active regeneration. Diesel engines of MY 2007 or newer often incorporate one or 

more of the following approaches: 

• On-board electrical heaters upstream of the filter. 

• Air-intake throttling in one or more of the engine cylinders. When necessary, this device 

would limit the amount of air entering the engine, raising the exhaust temperature and 

facilitating regeneration. 

• Exhaust brake activation. When necessary, this device would limit the amount of exhaust 

exiting the engine, raising the exhaust temperature and facilitating regeneration. 

• Engine speed increases. This approach is sometimes used in combination with the other 

approaches to deliver more heat to the filter to facilitate regeneration.

• Post top-dead-center (TDC) fuel injection. Injecting small amounts of fuel in the cylinders of 

a diesel engine after pistons have reached TDC introduces a small amount of unburned fuel 

in the engine’s exhaust gases. This unburned fuel can then be oxidized over an oxidation 

catalyst upstream of the filter or oxidized over a catalyzed particulate filter to combust 

accumulated particulate matter. 

• Post injection of diesel fuel in the exhaust upstream of an oxidation catalyst and/or catalyzed 

particulate filter. This method serves to generate heat used to combust accumulated 

particulates by oxidizing fuel across a catalyst present on the filter or on an oxidation catalyst 

upstream of the filter
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• On-board fuel burners upstream of the filter 18

These are presented here merely as examples, and are by no means a complete list of the

strategies available to manufacturers when designing engines that use automatic active DPF 

regeneration, though not all may be applicable to all engines. A common approach that gets a lot 

of consumer attention is the use of fuel burners or fuel injection strategies. This approach is 

often called “dosing.” Vehicle owners may notice an increase in fuel consumption when driving 

a vehicle that relies heavily on fuel dosing for its automatic active regenerations. In this case, 

when an engine’s ECM gives the signal, the doser injects a metered amount of diesel fuel into 

the exhaust flow (or cylinders), which reacts with the DPF catalyst to raise the temperature to a 

point that enables regeneration. EPA does not have information about which manufacturers 

employ this technique or the number or types of vehicles with engines that use fuel dosing as 

part of the active regeneration strategy. Estimates of the additional fuel use by a vehicle whose 

DPF regeneration system employs fuel dosing are described below in Section VII.B. This is also 

mentioned here because one of the possible outcomes of this EPA action is that some 

manufacturers may alter their strategies for automatic active regenerations on emergency 

vehicles, which may have a modest effect on supplemental fuel use due to dosing. Further 

discussion of this is provided below in Section VII.

(2) Why Are Emergency Vehicles Having Problems with DPF Regeneration?

At the time of promulgation of the heavy-duty highway rule, EPA and the engine 

manufacturers expected the 2007-compliant engine emission control systems would be integrated 

with advanced engine controls to ensure DPF regeneration under all vehicle operating conditions 

and environments. While this is widely true today, the experience of the rule implementation 

thus far indicates there are still some exceptions.

Although EPA is aware of a relatively small number of emergency vehicles that are 

experiencing problems with DPF regeneration, of those that are having problems, most of the 

problems can be related to the vehicle’s duty cycle, the ambient conditions, and/or the engine’s 

combustion characteristics. A vehicle’s duty cycle means how it is driven, including its speeds, 

loads, and distances, as well as time out of service and time spent idling. A vehicle’s duty cycle 

can vary by the demographic of the service area, including whether the vehicle responds to 

emergencies in a rural or urban community, and whether it drives over flat or hilly terrain. 

Because DPF regeneration requires heat and oxygen (basic ingredients for combustion), the 

success of DPF regeneration strategies can also be influenced by ambient conditions such as 

extreme cold winter temperatures and whether the vehicle operates near sea level or at a high 

elevation. The engine combustion and exhaust characteristics can influence the success of a DPF 

regeneration strategy since parameters such as engine-out NOX and PM emission levels can 

influence how easily the soot can be oxidized, and how much soot needs to be oxidized and how 

often. 

 

18 MECA Diesel Particulate Filter Maintenance: Current Practices and Experience (June 2005) 

http://www.meca.org/galleries/default-file/Filter_Maintenance_White_Paper_605_final.pdf 
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Both the engine’s duty cycle and the overall control strategy of the engine’s emission 

control system play a large role in the success of integrating a DPF with an engine to control PM 

emissions. In this section we provide additional discussion of how engine combustion 

characteristics and vehicle duty cycle can lead to DPF regeneration problems on emergency 

vehicles. In Section IV.E, below, we discuss our proposed regulatory action to address these 

issues. While our proposed approach specifically targets engine combustion characteristics and 

emission control system design, we encourage emergency vehicle owners to inquire with their 

dealers and manufacturers regarding suitable vehicle and engine options that are appropriate for 

their duty cycle as well as their demographic and geographic location. 

(a) Engine Combustion Characteristics 

Engine combustion characteristics can be designed to enable continuous passive 

regeneration or to rely heavily on automatic active regeneration. As mentioned above, 

regeneration is a combustion process, burning off the accumulated PM or soot. The PM is 

created because the initial combustion process in the engine was imperfect. To completely 

convert all fuel to CO2 and water, the combustion process needs more heat and oxygen. Both of 

these things create NOX because nitrogen (N2) is naturally present in the air and readily oxidizes 

at high temperatures. Thus there is a NOX-PM trade-off of most diesel combustion processes 

(homogeneous charge compression ignition being an exception) where lower combustion 

temperatures help control NOX but create more PM, and higher temperatures that destroy PM (or 

prevent it from being created) can generate more NOX. 

In an engine with a DPF system, combustion settings, or calibrations that enable 

continuous passive regeneration, tend to be those with higher engine-out NOX and lower engineout PM, partly because of the higher temperatures that create the NOX, partly because of the 

NOX itself that can act as an oxidizer (to burn off soot), and partly because of the lighter soot 

loading rate. In contrast, engine calibrations that may lead to a heavy reliance on automatic 

active regeneration tend to be those with lower engine-out NOX and higher engine-out PM, partly 

because of the lower temperatures, partly because of a lack of helpful NOX, and partly because of 

a heavier soot loading rate. Note that “engine-out” means emissions upstream of any aftertreatment cleaning devices such as DPF or SCR. An example of a DPF system that may rely 

almost exclusively on active regeneration to maintain a clean PM filter, from an engine 

calibration perspective, would be an engine using advanced exhaust gas recirculation, because it 

would have very low engine-out NOX and relatively high engine-out PM. An example of a DPF 

system that may rarely experience automatic active regeneration (and frequently passively 

regenerate), from an engine calibration perspective, would be an engine using SCR to control 

NOX, because it could have comparatively high engine-out NOX and relatively low engine-out 

PM. The SCR after-treatment would then reduce the high engine-out NOX to provide very low 

tailpipe NOX. 

Thus it is important to note that this NOX-PM trade-off is a critical design parameter 

when developing an engine that will be successfully integrated with a DPF-equipped emission 

control system. To date, all of the concerns expressed to EPA regarding emergency vehicles 

with DPF regeneration issues have been for vehicles that do not employ SCR technology, and 

thus may have higher engine-out PM. The differences in engine combustion characteristics of 
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the MY 2007 vehicles compared to those of the majority of MY 2010+ vehicles support the 

concept that the emergency vehicle fleet may experience fewer DPF regeneration troubles as it 

migrates to engines that use after-treatment to meet EPA’s 2010 NOX standards. Such a trend 

may indicate that some engine manufacturers may see a greater need to address in-use 

emergency vehicles than new vehicles. 

(b) Duty Cycles

As noted above, the duty cycle of a vehicle is one of the factors that influences how often 

the DPF regenerates passively or actively. It is important to note that all DPF systems with 

active regeneration components also have the capability to passively oxidize soot accumulated 

on the filter, though some of the above-described factors may inhibit successful passive 

regeneration. Operation at highway speeds and high engine loads (high load means demanding 

more work from the engine, such as accelerating, driving uphill or carrying heavy cargo) 

typically leads to successful passive regeneration of a DPF. An example from a duty-cycle 

perspective of a vehicle that frequently experiences automatic passive regeneration would be a 

long-haul tractor-trailer. There is also often a threshold of speed or load that is required for 

automatic active regeneration strategies as well, though not as great as for passive regeneration – 

often at least 5 miles/hour or parked with a PTO engaged. In some vehicles, passive 

regeneration occurs so rarely that a DPF system relies almost exclusively on active regenerations 

to maintain a clean PM filter. An example of this from a duty-cycle perspective would be a 

vehicle that operates at idle, low speed and low load over most of its duty cycle. Many 

emergency vehicles fall into this category.

It is possible to collect duty cycle data from trucks by extracting information that is 

broadcast by the engine’s ECM. ECM’s broadcast information such as engine speed, load, 

temperature, DPF backpressure, and many other parameters relevant to engine operation. In 

2004 the Fire Apparatus Manufacturers Association conducted a data-collection project, 

downloading logged data from emergency vehicles in use across the United States, to document 

duty cycles and engine conditions typically experienced in the emergency fleet, including 

pumpers, aerials, and rescue vehicles in urban, suburban and rural communities.19 The 2004 

FAMA data set includes 26 service months of data from 51 pumper trucks, 31 service months of 

data from 21 aerial trucks, and 14 service months of data from 4 rescue vehicles. Overall, the 

data reveal that emergency vehicles in urban centers log more hours than vehicles in suburban or 

rural areas, with the urban and suburban vehicles logging over five and four times the average 

rural engine hours, respectively, on an annual basis. This demographic data could be helpful to 

fleet managers who wish to understand why they have or have not experienced certain troubles 

with their vehicles. The data also indicate that vehicles with PTO capability (pumpers and 

aerials) operate in PTO mode on average about 10 percent of their operating time. Further, the 

data indicate the vast majority of emergency fleet operation is at loads below 10 percent of 

maximum capacity and engine speeds below 1,000 rpm. Data of this type could be helpful to 

engine manufacturers who may wish to assure that their emission control system designs will be 

 

19 Fire Apparatus Manufacturer’s Association, Fire Apparatus Duty Cycle White Paper, August 2004, available at 

http://www.deepriverct.us/firehousestudy/reports/Apparatus-Duty-Cycle.pdf
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successful for a given application. For the vehicles from which operating data were collected, 

FAMA determined an average engine load using the total horsepower, percent load, and percent 

time at load. Table IV-1 presents a summary of the engine load data compiled in FAMA’s study. 

Table IV-2 presents operating data by both vehicle type and demographic, and Table 

IV-3 presents an overview of the data by vehicle type. 

Table IV-1 FAMA Engine Load Data

Apparatus Type Capacity Range in 

Study 

Population Average 

Percent Running Load 

Pumper 315-500 hp 18 %

Aerial 170-500 hp 30 %

Rescue 350-500 hp 20 %
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Table IV-2 FAMA Duty Cycle Data by Demographic

Service 

Area

Operating Condition Pumper Aerial Rescue Service Area 

Average 

Rural Engine Hours (Avg Annual) 301 204 301 295

PTO Hours (Avg Annual) 70 63 - -

Low Speed (% Time < 1,000 RPM) 63 73 51 62a

Medium Speed (% Time 1,000 < RPM 

< 1,800)

27 19 42 29a

High Speed (% Time > 1,800 RPM) 11 9 7 9a

Low Load (% Time < 10%) 61 83 59 68a

Medium Load (% Time 10% < Load < 

90%) 

36 11 39 29a

High Load (% Time > 90%) 3 6 2 4a

Suburban Engine Hours (Avg Annual) 1364 1133 367 1272

PTO Hours (Avg Annual) 168 123b - -

Low Speed (% Time < 1,000 RPM) 71 68 77 72a

Medium Speed (% Time 1,000 < RPM 

< 1,800)

23 27 17 22a

High Speed (% Time > 1,800 RPM) 6 5 7 6a

Low Load (% Time < 10%) 54 37 78 56a

Medium Load (% Time 10% < Load < 

90%)

44 58 22 41a

High Load (% Time > 90%) 3 5 0 3a

Urban Engine Hours (Avg Annual) 1107 2379 1686 1681

PTO Hours (Avg Annual) 93 213b - -

Low Speed (% Time < 1,000 RPM) 62 73 57 64a

Medium Speed (% Time 1,000 < RPM 

< 1,800)

32 22 32 29a

High Speed (% Time > 1,800 RPM) 5 5 11 7a

Low Load (% Time < 10%) 73 53 44 57a

Medium Load (% Time 10% < Load < 

90%)

24 42 51 39a

High Load (% Time > 90%) 3 5 5 4a

Notes:

a Straight average by EPA from summary results. Other values in this table are weighted averages compiled by 

FAMA using individual vehicle data

b Includes both pumping and aerial operating hours
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Table IV-3 FAMA Duty Cycle Data by Vehicle Type

Operating Condition Pumper Class 

Average 

Aerial Class 

Average 

Rescue Class 

Average 

Fleet Average

Engine Hours (Avg Annual) 924a 1239a 785a 1244

PTO Hours (Avg Annual) 117b - -

Low Speed (% Time < 1,000 

RPM) 66 71 61 67 

Medium Speed (% Time 1,000 

< RPM < 1,800) 27 23 30 26 

High Speed (% Time > 1,800 

RPM) 7 5 9 7 

Low Load (% Time < 10%) 62 50 56 58

Medium Load (% Time 10% < 

Load < 90%) 35 45 41 38 

High Load (% Time > 90%) 3 5 3 3

Notes:

a Straight average by EPA from summary results. Other values in this table are weighted averages compiled by 

FAMA using individual vehicle data

b Includes only pumping hours. Aerial operating hours averaged 69 hours per year.

We can see from this study that engines on emergency vehicles across the country are 

commonly operated over duty cycles that offer very limited opportunities to regenerate DPF’s. It 

is also important to note that emergency vehicles do not typically get deployed on planned duty 

schedules with predictable blocks of garage time for servicing or maintenance. While some 

other types of vocational vehicles may have duty cycles with many characteristics similar to 

those shown above, emergency vehicles are unique in their need to be ready to deploy at any 

moment for the purpose of protecting public safety and welfare by saving human lives that may 

be in immediate danger. 

When trucks with an engine-driven PTO are working in a stationary PTO mode, some 

engines achieve the conditions to enable an automatic active regeneration during this time. 

While this is normally designed to be a transparent process, in practice some effects of this type 

of regeneration have been noticed by operators. EPA has received information from fire chiefs 

indicating that there have been instances where engine ECM’s took control from the operator 

during water pumping operations. When an automatic active regeneration is initiated during a 

water pumping operation, for example, an ECM may be programmed to alter throttle position or 

engine speed to achieve the conditions needed to complete an automatic active regeneration. 

Depending on the design of the water pumping system’s pressure regulation, this may in turn 

affect the water pressure in the fire hoses. EPA has not heard of this occurring on a widespread 

basis, and has reason to believe that affected engine and truck manufacturers have identified and 

corrected this issue on some vehicles. EPA’s current regulations already allow manufacturers to 

develop and request EPA approval for certification of engines with emission control strategies 

where the process of undergoing automatic active regeneration would not interfere with safely 

pumping fire suppressant. EPA requests comment on whether any EPA action should be taken 

to explicitly address this situation beyond what we are already proposing in this action. 
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While not addressed directly in this proposed action, there are technologies that could be 

implemented to decrease the amount of time emergency vehicles spend with their main engines 

operating at light loads and at idle. These technologies include electronically programmed 

automatic engine start/stop systems and hybrids. Automatic start/stop systems automatically 

stop and start an engine depending upon whether or not it is needed to supply power to the 

vehicle. This technology is already being implemented on other heavy-duty vehicles to decrease 

unnecessary engine idling. Hybrid drivetrains also decrease engine idling with an integrated 

alternate power source such as a battery. We are currently seeing an increase in the use of hybrid 

technologies in heavy-duty diesel vocational vehicles. Garbage trucks, utility company trucks, 

and other work trucks are using hybrid technology to power on-board hydraulic systems and cab 

heating and cooling systems. In conventional vehicles these systems are powered by a main

engine typically operating at light load or at idle. Because automatic start/stop and hybrid 

technologies improve fuel economy and decrease greenhouse gas emissions, we believe that they 

will be used in more and more vehicles in the future. We believe there is potential for these 

technologies to be integrated into future designs of emergency vehicles to decrease their 

operation at light loads and at idle. Such technologies would not only improve fuel economy and 

decrease greenhouse gas emissions from emergency vehicles, they would also help to prevent 

their diesel particulate filters from becoming plugged due to excessive operation at light loads 

and at idle. While we are not proposing any specific action at this time related to decreasing the 

amount of time emergency vehicles operate at light load or at idle, we request comment on the 

potential for application of alternate power sources and idle reduction technologies on 

emergency vehicles.

(3) What Are the Concerns for Emergency Vehicles Using SCR?

Selective Catalytic Reduction (SCR) is an exhaust after-treatment system used to control 

NOX emissions from heavy-duty engines by converting NOX into nitrogen (N2) and water (H2O). 

The technology depends on the use of a catalytic converter and a chemical reducing agent, which 

generally is in an aqueous urea solution, and is often referred to as diesel exhaust fluid (DEF). 

Some trade names for this chemical reductant include AdBlue, BlueDef, NOxBlue, and 

TerraCair.

Most engine manufacturers chose to comply with the 2010 NOX emission standard by 

adding SCR to their engine models. In general, the approach with an SCR system has been a 

sound and cost effective pathway to comply with EPA’s 2010 emissions standards, and it is the 

primary path being used today. 

DEF is injected into the exhaust upstream of the SCR catalyst where it forms ammonia 

and carbon dioxide. The ammonia then reacts with NO and NO2, so that one molecule of urea 

can reduce two molecules of NO or one molecule of NO2. A robust SCR system can achieve 

about 90 percent reduction in cycle-weighted NOX emissions. Improvements have been made 

over the last several years to improve the NOX conversion rate and reduce the impact of lower 

exhaust temperatures on the conversion efficiency. 

Because an SCR system is only effective when DEF is injected into the exhaust, we 

consider refilling a vehicle’s DEF tank to be a critical emission-related engine maintenance 

requirement. We are taking action elsewhere in this notice (See Section V) to establish this in 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

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our regulations. Therefore, manufacturers have implemented a number of strategies to induce a 

vehicle operator to refill a vehicle’s DEF tank when needed. These operator inducements 

generally include first illuminating one or more dashboard lights to warn the operator that the 

DEF tank needs to be refilled soon. However, if such initial inducements are persistently 

ignored by the vehicle operator, eventually additional inducements are typically activated that 

decrease the maximum speed or power of the vehicle. These additional inducements are 

intended to create conditions making operational conditions of the vehicle increasingly 

unacceptable if the initial dashboard lamp illumination inducements are persistently ignored. 

Similar inducements may occur in cases where DEF quality does not meet system specifications, 

or if the SCR system is not functioning correctly for another reason. 

While decreasing vehicle performance can be an effective inducement strategy, we 

believe it may not be appropriate in all situations for emergency vehicles because of their special 

need to be ready at any moment for the purpose of protecting public safety and welfare by saving 

human lives that may be in immediate danger. We recognized this during the initial 

implementation of our 2010 NOX standards, and we worked with the Fire Apparatus 

Manufacturers’ Association (FAMA), the Ambulance Manufacturers Division of the National 

Truck Equipment Manufacturers Association, and the International Association of Fire Chiefs to 

support the publication of a May 18, 2010 memo that instructed emergency vehicle 

manufacturers and engine manufacturers to implement less severe inducement strategies for 

emergency vehicles.20 In this proposal we are taking additional steps so that emergency vehicle 

manufacturers and engine manufacturers have the option to further reduce the severity or 

eliminate altogether any performance related inducements that are or could be implemented on 

emergency vehicles and their engines during emergency situations. We believe that this 

additional flexibility will help to prevent any abnormal condition of a vehicle’s emission control 

system from adversely affecting the speed, torque, or power of an emergency vehicle during 

emergency situations. 

D. What Would Occur if EPA Took No Action?

(1) The Industry Would Continue to Get Smarter

Improving the components of diesel particulate filters is the current subject of research 

and development activities within the automotive and air pollution control industries. Aspects 

that are being improved include filter ash storage capacity, filter pressure drop, substrate 

durability, catalyst activity, as well as other physical and chemical properties that can optimize 

the device for heavy-duty vehicle applications. 

Engine manufacturers have taken a systems approach, optimizing the engine with its 

after-treatment system to realize the best overall performance possible. Manufacturers can 

manage the functioning of the emission control system by adjusting parameters such as the 

thermal profile of the after-treatment system, the exhaust gas chemical composition, the rate of 

 

20 FAMA 2010, Emergency Vehicle SCR and DEF Inducement Guidelines; 2010 Engine Emissions Control 

Requirements
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consumption of DEF, the rate of particle deposition, and the conditions under which DPF 

regenerations (soot cleaning) may occur. 

In a broad and general sense, the trend is that DPF’s are slowly becoming even more 

robust without EPA intervention. Future DPF’s will need fewer total regenerations during the 

useful life of the engine and control system, more passive and fewer active regenerations will 

occur, and manual regenerations will become rarer. 

In addition, vehicle operators and fleet managers will continue to become more 

experienced with this new generation of sophisticated electronically-controlled vehicles. 

Manufacturers across the country are providing training on actions fleet managers can take to 

decrease problems with DPF regenerations. These actions include: 

• Use low-ash engine oils

• Avoid extended idling 

• Maintain insulation on the exhaust pipe 

• Maintain the crankcase filter

• Periodically operate a vehicle at higher speeds and loads

The Technology & Maintenance Council (TMC) of the American Trucking Associations 

conducted a survey in late 2011 to compare user experiences between EPA 2010, EPA 2007, and 

EPA 2004 vintage trucks. 21 According to TMC, 72 percent of the survey respondents indicated 

that driver understanding of the 2007-vintage after-treatment system was worse than driver 

understanding of the 2004-vintage after-treatment system, and 33 percent of respondents 

indicated that driver understanding of the 2010-vintage after-treatment system was worse than 

driver understanding of the 2007-vintage after-treatment system. The responses regarding driver 

understanding of fault codes and dash lamps indicated that drivers have 69 percent poorer 

understanding of 2007 vs. 2004 fault codes and dash lamps, and 50 percent poorer understanding 

of 2010 vs. 2007 fault codes and dash lamps. We expect that this education component will 

gradually improve over time without EPA intervention. 

(2) The Fleet Would Continue to Migrate to the 2010 Standards 

Vehicles with 2010-compliant heavy-duty diesel engines tend to place different demands 

on their DPF systems than pre-2010 vehicles. With the addition of NOX after-treatment such as 

SCR, engines may be tuned to emit lower engine-out PM (recall the NOX-PM trade-off described 

above). When an SCR system is integrated, it provides the opportunity to run an engine at lower 

soot levels and elevated levels of NO2, which is a chemical species that efficiently oxidizes the 

soot in the absence of elevated temperatures. It is EPA’s expectation that vehicles of MY 2010 

and beyond, particularly those using SCR, will generally experience fewer troubles with DPF’s 

 

21 American Trucking Associations, Technology & Maintenance Council, S3 Engine Study Group. Survey

conducted Fall 2011, public slides dated February 2012 available at 

http://www.truckline.com/Federation/Councils/TMC/Documents/2012%20Annual%20Meeting%20and%20Exhibiti

on%20Documents/TMC12A_TECH2.pdf
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than the earlier model year vehicles, due to the nature of the on-board technology as well as the 

many years of experience gained by manufacturers since 2007. The 2011 TMC survey included 

an assessment of relative satisfaction levels between EPA 2010, EPA 2007, and EPA 2004 

vintage trucks. The survey results indicate that after-treatment durability is better with EPA 

2010 trucks compared to EPA 2007 trucks, with less time out of service.22 As an illustration, 

according to a Volvo product brochure, the company’s EPA 2010-compliant trucks eliminate the 

need for active DPF regeneration, reducing driver involvement with the emission control system, 

using a design that allows for the DPF system to reliably oxidize accumulated soot using 

continuous passive regeneration.23

(3) Some Trucks Would Continue to Experience Problems

Even though such trends would indicate that instances of emergency vehicles 

experiencing difficulty managing regeneration of DPF’s would decrease, in the absence of this 

EPA action, some vehicles would be likely to continue to experience some problems. 

EPA has learned that some engine manufacturers have disabled these engine protection 

measures on some emergency vehicles. In these cases the manufacturer has reasoned that an 

operator should be allowed to remain in control of an emergency vehicle even facing risk of 

catastrophic failure, with the consequences of that failure being less severe than the 

consequences of the vehicle prematurely losing power, torque and/or speed while performing 

emergency services.

Without a clear action from EPA to provide the regulatory flexibility needed for swift 

deployment of robust remedies throughout the emergency vehicle fleet, implementation of best 

practices could be inconsistent, insufficient, or even impossible due to regulatory constraints. 

Some vehicles would continue to experience frequent plugging of DPF’s, frequent forced filter 

regenerations, and reduced engine power, speed or torque that diminish the ability of first 

responders to save lives and property. There would also remain a heightened risk that an 

emergency vehicle could be taken out of service when it is most needed. 

E. Proposed Regulatory Action

As described above in Section IV.C, many DPF-equipped vehicles include engine 

controls and driver alerts that lead to decreases in maximum speed, torque, or power when DPF 

backpressure exceeds normal levels, as protective measures for either the engine or the DPF, or 

as inducements for the operator to immediately conduct DPF regeneration. Similarly, vehicles 

equipped with selective catalytic reduction (SCR) systems for NOX reduction currently have 

engine controls and driver alerts that lead to eventual loss of speed, torque, or power when the 

SCR controls detect abnormal conditions (such as a malfunction, low DEF levels, etc.), as 

 

22 See ATA/TMC, Note 21. 23 See Volvo 2010 product brochure, “Volvo’s SCR No Regen Engine,” available at 

http://www.volvotrucks.com/SiteCollectionDocuments/VTNA_Tree/ILF/Products/2010/09-

VTM075_NoRegen_SS_041609.pdf
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inducements to take immediate corrective action to allow the SCR to function normally. In most 

vehicles, these alerts and inducements may be easily avoided with normal driving and routine 

maintenance, and if activated, these inducements would not have any significant effect on public 

safety and welfare. In emergency vehicles, however, should any of these limits on maximum 

speed, torque, or power occur while a vehicle is responding to an emergency, it could be a matter 

of life or death. To address these issues that could otherwise limit the maximum speed, torque or 

power of an emergency vehicle’s engine when it is needed most, EPA is proposing to amend 40 

CFR part 86 to revise the definition of defeat device; add new definitions of emergency vehicle, 

ambulance and fire truck; and add new labeling requirements for new on-highway engines with 

approved Auxiliary Emission Control Devices for emergency vehicles. EPA is also amending its 

regulations at 40 CFR part 1039 to revise the definition of defeat device, add a new definition of 

emergency equipment, and add a new labeling requirement for nonroad engines with approved 

Auxiliary Emission Control Devices for emergency equipment.

In our current regulations, engine manufacturers may request as part of an application for 

new engine or vehicle certification, and EPA may approve, Auxiliary Emission Control Devices, 

if they are not determined to be “defeat devices.” Auxiliary Emission Control Devices, or 

AECD’s, are any design element of an engine’s emission control system that senses temperature, 

vehicle speed, engine RPM, transmission gear, manifold vacuum, or any other parameter for the 

purpose of activating, modulating, delaying, or deactivating the operation of any part of the 

emission control system.24 Some AECD’s can temporarily decrease the effectiveness of an 

emission control system. This type of AECD is only permitted in very limited situations, for 

example, when such excursions are deemed to be necessary in order to protect the vehicle, 

engine, and or emission control system during limited modes of operation. 

A defeat device is a type of AECD that reduces the effectiveness of vehicle emission 

controls in situations when such reduction in effectiveness is not approved or permitted by EPA. 

Defeat devices are not permitted by the Clean Air Act or EPA. 

Approvals of AECD’s are made by EPA on a case-by-case basis. In applications for 

engine certification, manufacturers must include a detailed description of each AECD to be 

installed in or on any vehicle (or engine) covered by the application, as well as a detailed 

justification of each AECD that results in a reduction in effectiveness of the emission control 

system. According to 40 CFR 86.094-21(b)(1)(i)(B), EPA may disapprove a request for an 

AECD based on consideration of currently available technology. Use of an unauthorized or 

disapproved AECD can be considered a violation of section 203 of the Act.25

In this action, EPA is proposing to revise the definition of defeat device at 40 CFR 

86.004-2, 86.1803-01, and 40 CFR 1039.115 to exclude AECD’s that apply only for engines on 

emergency vehicles, where the need for an AECD is justified in terms of preventing the vehicle 

or equipment from losing speed, torque, or power due to abnormal conditions of the emission 

 

24 See 40 CFR 86.082-2 25 See 40 CFR 86.094-21 and 094-22
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control system, or in terms of preventing such abnormal conditions from occurring during 

operation related to emergency response. 

In this action, EPA is proposing to define an emergency vehicle as a vehicle that is an 

ambulance or a fire truck. EPA is proposing to adopt a definition of ambulance consistent with 

the current U.S. General Services Administration Star of Life specification.

26 EPA is proposing 

to define fire truck as a vehicle designed to be used under emergency conditions to transport 

personnel and equipment and to support the suppression of fires and mitigation of other 

hazardous situations, consistent with the scope of standards for automotive fire apparatus issued 

by the National Fire Protection Association.27 We are defining emergency equipment as 

specialized vehicles to perform aircraft rescue and firefighting functions at airports, or wildland 

fire apparatus. With these definitions, it is EPA’s intent to include vehicles that are purpose-built 

and exclusively dedicated to firefighting, emergency/rescue medical transport, and/or performing 

other rescue or emergency personnel or equipment transport functions related to saving lives and 

reducing injuries coincident with fires and other hazardous situations. EPA requests comment on 

whether we should refine or expand our definition of emergency vehicle within the scope of this 

action to include those equipped with heavy-duty diesel engines that serve other civilian rescue, 

law enforcement or emergency response functions. We are especially interested in information 

regarding instances of such vehicles experiencing or risking loss of power, speed or torque due to 

abnormal conditions of the emission control system, and how that may inhibit mission-critical 

life- and property-saving work. 

EPA is also proposing an associated engine labeling requirement so that engines with 

approved emergency vehicle AECD’s would be clearly identified and distinguished from other 

similar engines.

As mentioned above in Section IV.C, some engine manufacturers currently specify that 

when an engine is sold for installation in an emergency vehicle, some of the default power, 

torque or speed inducements be de-activated or set to alternate, less severe settings. In such 

applications, when the DPF system requests regeneration, the warning lights remain illuminated 

while the vehicle remains in complete control of the driver. In these cases the manufacturer has 

likely reasoned that the consequences of catastrophic failure would be less severe than the 

consequences of the vehicle prematurely losing power, torque and/or speed while performing 

emergency services. EPA has granted related AECD’s in the past. 

However, without the proposed optional flexibilities provided by EPA in this action, 

manufacturers could be prevented from implementing truly failsafe solutions for all affected 

vehicles. For example, while current custom solutions may allow an emergency vehicle to 

 

26 U.S. General Services Administration, Federal Specification for the Star-of-Life Ambulance, August 1, 2007, 

http://www.deltaveh.com/f.pdf. 27 See National Fire Protection Association web page. Accessed April 2012 at 

http://www.nfpa.org/catalog/product.asp?title=Code-1901-2009-Automotive-FireApparatus&category%5Fname=&pid=190109&target%5Fpid=190109&src%5Fpid=&link%5Ftype=search&icid=
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continue pumping water or transporting a person to safety, its DPF would continue to accumulate 

particles and the risk of catastrophic failure would increase.

In this action, EPA is proposing amendments so that manufacturers could apply for (and 

EPA could approve) AECD’s that would be justified in terms of preventing the occurrence of 

abnormal conditions of the emission control systems for emergency vehicles or in terms of 

preventing the engines from losing speed, torque, or power due to such abnormal conditions. In 

this context, EPA would consider abnormal conditions to be parameters outside normal ranges 

for proper operation, such as excessive exhaust backpressure from high soot loading on a DPF or 

insufficient DEF for use with an SCR system. 

EPA is encouraging manufacturers to apply for AECD’s that are tailored for engines on 

emergency vehicles, considering the duty cycle information presented above in Section 

IV.C(2)(b) along with any other information needed to design failsafe emission control systems

for new emergency vehicles. EPA is also encouraging manufacturers to design field 

modifications to address these issues on in-use emergency vehicles, including those whose 

engines are no longer in production. Further discussion of field modifications is provided below 

in Section IV.F(2). 

To achieve these goals, EPA understands that increased flexibility would be needed

because EPA’s strict NOX and PM standards present many design constraints. Below we 

describe some solutions that EPA believes it could approve as part of an emergency vehicle 

AECD or field modification, as proposed. Upon adoption of these amendments, EPA would 

encourage requests by engine manufacturers for emergency vehicle AECD’s and/or field 

modifications for in-use emergency vehicles for which service disruptions related to abnormal 

conditions of emission control systems may occur or have occurred. EPA suggests that such 

AECD’s or field modifications could include, but are not limited to, one or more of the following 

strategies: 

(1) Liberalized Regeneration Requests

It is current practice that most modern diesel engine ECM’s are set to initiate an 

automatic active regeneration only above a designated DPF soot load, and those vehicles 

equipped with manual regeneration switches are set to not allow the option of initiating manual 

active regeneration until an even greater soot load is detected. The reason why manufacturers do 

this is related to certification of engine families and vehicle test groups. If manufacturers can 

limit the frequency of regenerations by design, then they can be assured that average emissions 

will remain below the certified average emission level. Excess regenerations could lead to 

higher average emissions, since some exhaust emissions increase during regeneration. 

Particularly for engines not equipped with SCR systems, NOX emissions can increase by an 

order of magnitude during regeneration, and these temporary increases in emission are accounted 

for in EPA’s certification process. See Section VII, below, for more information about the 

emissions impacts of DPF regenerations. In addition, excess regenerations could shorten the 

useful life of the DPF system since high temperatures place stress on filter substrates. 

EPA believes that emergency vehicle AECD’s that enable more frequent automatic active 

and manual active DPF regenerations, associated with a wider range of soot loads could improve 
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the reliability of DPF systems without significantly compromising emissions reductions or 

durability. As explained below Section IV.F(4), EPA does not expect this provision to affect 

other aspects of certification. For emergency vehicles with approved AECD’s that involve 

changes in the frequency of regeneration, EPA proposes that the resulting increase in NOX

emissions not be counted against certification levels for applicable engine families or vehicle test 

groups. Furthermore, EPA proposes that emissions certification testing be conducted with any 

approved AECD’s for emergency vehicle or equipment deactivated. According to EPA’s current 

engine certification data, engines from MYs 2008 and 2011 have an average maximum 

automatic active regeneration frequency near 20 percent, with the typical frequency between 

three and seven percent. Those with frequencies near zero rely almost exclusively on passive 

regeneration.28 EPA requests comment on whether an option for more frequent automatic active 

and/or manual active DPF regenerations for emergency vehicles would be beneficial for 

reliability of those DPF systems, and whether EPA should apply any constraints on the 

frequency of manual active DPF regenerations when approving AECD’s for emergency vehicles. 

(2) Engine Recalibration 

As mentioned above, in-cylinder combustion chemistry dictates a NOX-PM trade-off 

where engines calibrated to reduce in-cylinder NOX tend to have higher PM levels. These factors 

lead to higher rates of particle accumulation and lower rates of particle oxidation on filters. EPA 

believes that AECD’s that incorporate engine calibration modifications could enable operation in 

a “low soot mode” with a reduced rate of particle deposition that would lead to more frequent 

and effective passive regenerations. Such calibration modifications could also extend the 

operating time between all types of regenerations, improve active regeneration effectiveness, and 

boost reliability of the DPF systems. On engines with downstream (i.e., SCR) NOX controls, 

SCR control could be modulated such that engine recalibration would not significantly affect 

NOX emissions. On engines without downstream NOX controls, EPA believes that some degree 

of increased NOX emissions during the conditions justified by the AECD would be approvable 

for emergency vehicles. As explained below in Section IV.F(4), EPA does not expect this 

provision to affect other aspects of certification. When manufacturers calculate the average NOX

emissions during a test cycle, they incorporate data regarding both the frequency of regeneration 

and the increase in NOX emissions during regeneration. For emergency vehicles with approved 

AECD’s that involve recalibration to alter regeneration frequency or average NOX emissions, 

EPA proposes that the resulting increase in NOX emissions not be counted against certification 

levels for applicable engine families or vehicle test groups. Furthermore, EPA proposes that 

emissions certification testing be conducted with any approved AECD’s for emergency vehicle 

or equipment deactivated. A discussion of the estimated emissions impacts of recalibration is 

found below in Section VII.B. EPA requests comments on whether an upper limit of average 

NOX emissions - considering regeneration frequency and duration, peak NOX emission rate, and 

operating conditions under which the AECD is triggered - should be established as part of the 

implementation of this AECD option, and what levels may be appropriate. 

 

28 Frequency in percent refers to the fraction of engine test cycles during which an automatic active regeneration 

occurs.
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(3) Backpressure Relief

It is EPA’s objective that all of our clean diesel emissions standards be implemented with 

reliable technologies that require a minimum amount of driver intervention and do not 

compromise the utility of vehicles. EPA understands that manufacturers are motivated to seek 

design solutions that are cost effective and easily deployable. However, by focusing solely on 

preventive measures such as those described above, manufacturers may not achieve a completely

failsafe DPF strategy on all emergency vehicles. EPA anticipates that some vehicles may benefit 

from an additional failsafe measure that relieves engine exhaust backpressure as a last resort to 

prevent loss of engine speed, torque or power. There are products on the market today that could 

be configured to temporarily relieve excessive engine exhaust backpressure when detected, then 

return the system to normal at the instant that backpressure returns to a safe level. Such a device 

may be justified as a failsafe measure, and may be included as part of an overall strategy that 

also includes preventive measures, if justified and properly limited, where excess PM emissions 

would be expected to be emitted only during a small fraction of vehicle operation. That is, the 

vast majority of DPF operating cycles would be expected to have continuous PM emission 

control, while any temporary backpressure relief that reduced PM control or allowed bypass of 

controls would be expected relatively infrequently. EPA requests comment on whether a failsafe 

measure to provide engine exhaust backpressure relief should be available as an approvable

AECD option, and what constraints, if any, should be established for this option. 

F. What Engines and Vehicles Would be Affected?

Today’s proposal would apply to new and in-use fire trucks and ambulances, new and inuse airport fire apparatus and wildland fire apparatus, and heavy-duty diesel engines on these 

emergency vehicles and equipment. 

(1) Newly Certified Engines and Vehicles

Of those new diesel engines covered by EPA’s current heavy-duty diesel standards, only 

those installed in vehicles or equipment meeting the definition of emergency vehicle or 

emergency equipment would be eligible to obtain an approved AECD of the type discussed 

above in Section IV.E. Where a vehicle is chassis-certified and either sold as an incomplete 

vehicle to a truck body manufacturer or built and sold as a complete vehicle, only those sold and 

built as emergency vehicles would be eligible to obtain an approved AECD of the type discussed 

above in Section IV.E. 

(2) Certified Engines and Vehicles In-Use

To address in-use engines and vehicles, EPA proposes to allow engine and vehicle 

manufacturers to submit requests for EPA approval of Emergency Vehicle Field Modifications 

(EVFMs) for on-highway emergency vehicles and Emergency Equipment Field Modifications 

(EEFMs) for nonroad emergency equipment. EVFMs and EEFMs would be modifications to

existing hardware and software to be installed on in-use vehicles or equipment to prevent loss of 

speed, torque, or power due to abnormal conditions of emission control systems, or to prevent 

such abnormal conditions from occurring, during vehicle or equipment operation related to 

emergency response. EPA proposes to use an approval process similar to the process that is 
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currently utilized to submit modifications to current applications for certification, also known as 

“running changes.” The information submitted by a manufacturer to EPA as part of this request 

and approval process would be similar to the information submitted for emergency vehicle or 

equipment AECD’s. 

 It is important to emphasize that this proposal would allow only those approved 

modifications to be deployed by manufacturers and their authorized dealers. Modifications made 

by end users are not generally approvable; rather the tampering prohibitions would generally 

apply to such modifications. 

EPA has identified three types of field modifications that would be permitted for 

emergency vehicles and emergency equipment under the proposed regulations, based on the 

extent to which the modification is being incorporated into new production vehicles and 

equipment. The three types are: 

• Type A: Any field modification that is a change to a certified vehicle (i.e., a vehicle, 

engine or equipment covered by a certificate of conformity) that is identical in all 

respects to a running change that is approved for incorporation in new vehicles by the 

manufacturer. Where the running change was approved by EPA for implementation only 

in conjunction with certain other running changes, the field modification may be 

considered to be a Type A field modification only if implemented under the same 

constraints. 

• Type B: Any field modification that is not identical in all respects to, but provides for 

essentially the same purpose as, a running change that is being incorporated in new 

vehicles by the manufacturer or that would have been incorporated if the vehicle were 

still in production. A Type B field modification is used when it is not practical to 

incorporate the exact running change in vehicles that have left the assembly line, or when 

the vehicles are no longer in production. 

• Type C: Any field modification that is made selectively only to vehicles which have left 

the assembly line and which would not have been incorporated on the assembly line. For 

example, this would apply when making a field modification to a vehicle that is no longer 

in production where there are no similar vehicles in production. 

The amount of justification needed for the field modification differs depending on which 

type of modification is being requested. 

(3) Labeling Requirements

Because the engines and vehicles eligible for the AECD’s described in this proposal 

belong to broadly certified engine families and test groups, when they are sold for installation in 

an emergency vehicle and equipped with one or more approved emergency vehicle AECD’s, 

they must be labeled as such, to distinguish them from other certified engines. EPA is proposing 

adding a labeling requirement to 40 CFR part 86 subpart A, such that engines with one or more 

approved AECD’s for emergency vehicle applications must be labeled with the statement: “THIS 

ENGINE IS FOR INSTALLATION IN EMERGENCY VEHICLES ONLY.” EPA is also 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

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proposing adding a labeling requirement to 40 CFR part 86 subpart S, such that vehicles with 

one or more approved AECD’s for emergency vehicles, include the following statement on the 

emission control information label: “THIS VEHICLE HAS A LIMITED EXEMPTION AS AN 

EMERGENCY VEHICLE.” EPA is also adding a labeling requirement to 40 CFR part 1039, 

such that nonroad engines with one or more approved AECD’s for emergency equipment include 

a label with the following statement: “THIS ENGINE IS FOR INSTALLATION IN 

EMERGENCY EQUIPMENT ONLY.”

EPA requests comment on whether these labeling requirements are satisfactory to ensure 

that engines and vehicles operating with approved emergency AECD’s are permanently 

distinguished from similar certified engines. EPA also requests comment on whether a similar 

label should be required for an in-use emergency vehicle or equipment where a field 

modification is deployed that prevents the engine from losing speed, torque, or power due to any 

occurrences of abnormal conditions of the emission control system, or prevents such abnormal 

conditions from occurring.

(4) Other Regulatory Provisions

Today’s proposal would not alter the tampering prohibition in 40 CFR 1068.101(b)(1). 

This provision describes a general prohibition against anyone from removing or rendering 

inoperative an engine’s emission controls before or after entering into service, where an 

exception is provided in 1068.101(b)(1)(ii) for engine modifications needed to respond to a 

temporary emergency, provided that the engine is restored to proper functioning as soon as 

possible after the emergency has passed. EPA encourages manufacturers to design their 

emergency vehicle AECD’s to be engaged only to the extent necessary to prevent the engine 

from losing speed, torque, or power due to abnormal conditions of the emission control system, 

or to prevent such abnormal conditions from occurring during operation related to emergency 

response. EPA recognizes that there may be cases where an AECD may need to be engaged at 

times other than while actively responding to an emergency, in order to assure that loss of speed, 

torque or power does not occur during operation related to emergency response. EPA also 

recognizes that some AECD’s may involve electronic approaches where the engine’s functions 

would be modulated based on exhaust backpressure or other parameters that are not correlated 

with any emergency situation. EPA may even, in extreme cases, such as at high altitude or with 

certain older MY engines allow engagement of AECD’s at all times, if they are justified as 

necessary to prevent engine from losing speed, torque, or power during operation related to 

emergency response. 

We would also encourage manufacturers to design their emission control systems to 

discourage tampering. According to EPA’s tampering prohibition, a vehicle operator who 

abuses or alters an approved AECD may be guilty of tampering. For example, if an AECD 

includes enabling an operator to initiate more frequent manual active regenerations, engine 

manufacturers may choose to prevent the abuse of this function by means such as a daily or 

weekly cap on the number of manual active regenerations, or a minimum soot loading for the 

function to engage. As another example, if an emergency vehicle alerts a driver to an abnormal 

condition of its emission control system by illuminating dash lamps, alarms or other warnings 

that do not limit vehicle performance, it is the operator’s responsibility to take prompt action to 
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remedy the problem.29 If an operator disregards such warnings beyond the time needed to 

respond to the emergency, this may be considered tampering. It is important to note that if an 

emergency vehicle is not equipped to ever allow an operator to initiate a manual active 

regeneration, this may in practice encourage tampering by the end user. 

Manufacturers of highway and nonroad engines would be required to describe any 

emergency vehicle AECD in an application for certification. In this action, we are not proposing 

any revisions to the information needed to review and approve AECD’s. It is common practice 

for manufacturers, in describing AECD’s, to identify engine parameters such as those that would 

operate differently to preserve adequate engine performance during an emergency, including 

information about how the engine would respond under different in-use operating conditions 

under the various sets of conditions that would otherwise cause the engine to operate at less than

full performance levels. Other than the requirement for a manufacturer to describe the emergency 

vehicle AECD in its application for certification, we do not expect this provision to be relevant 

for other aspects of certification. For example, EPA proposes that emissions certification testing 

be conducted with any approved AECD’s for emergency vehicle or equipment deactivated. 

Additionally, manufacturers would not need to consider emergency vehicle AECD’s when 

developing infrequent regeneration adjustment factors (IRAFs) or when developing deterioration 

factors (DFs). Thus, EPA proposes that manufacturers could include emergency and nonemergency engines and vehicles in the same engine families and test groups. EPA also proposes 

that manufacturers may apply for emergency vehicle AECD’s for new, existing, and/or formerly 

approved emissions certificates. EPA requests comments on this aspect of the proposal. 

V. Scheduled Maintenance and Maintenance Interval for 

Replacement of Diesel Exhaust Fluid

EPA is proposing to include new provisions in its regulations that explicitly permit 

replacement of diesel exhaust fluid (DEF) as part of approved emission-related scheduled 

maintenance and set out the permitted maintenance intervals for replacement of DEF on diesel 

fueled new motor vehicles, new motor vehicle engines and new nonroad compression-ignition 

(NRCI) engines.

A. Background

EPA’s regulations define the emission-related scheduled maintenance that may be 

performed for purposes of durability testing and for inclusion in maintenance instructions 

provided to purchasers of new motor vehicles and new motor vehicle engines. See 40 CFR 

86.094-25(b); 40 CFR 86.004-25(b); 40 CFR 86.1834-01(b). The regulations include lists of 

emission-related maintenance and intervals for this maintenance. See 40 CFR 86.004-25(b)(4); 

40 CFR 86.1834-01(b)(4). For example, in general, the maintenance interval for the adjustment, 

 

29 Although this action would not affect certification of engine families or test groups, EPA’s regulations do offer 

options to manufacturers who wish to ensure that emission-related maintenance will occur in use, including visible 

signals that are not reset until maintenance occurs. 40 CFR 86.004-25(b)(6)(ii).
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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cleaning, repair of the following items is 100,000 miles of use, and then at 100,000 mile intervals 

thereafter for diesel cycle light-duty vehicles, diesel cycle light-duty trucks, and light heavy-duty 

diesel engines and at 150,000 mile intervals for medium and heavy heavy-duty diesel engines: 

fuel injectors, turbochargers, electronic engine control units, particulate trap or trap-oxidizers, 

exhaust gas recirculation systems, and catalytic converters. The regulations also include a 

procedure that allows manufacturers to request a different maintenance schedule or to request 

new scheduled maintenance, which includes maintenance that is a direct result of the 

implementation of new technology not found in production prior to the 1980 model year. See 40 

CFR 86.094-25(b)(7); 40 CFR 86.1834-01(b)(7). 

Similarly, EPA’s regulations applicable to nonroad compression-ignition (NRCI) engines 

define the emission-related maintenance that may be performed for purposes of providing 

ultimate purchasers written instructions for properly maintaining and using the engine. Such 

emission-related maintenance and associated intervals apply to service accumulation on 

emission-data engines. See 40 CFR 1039.125. This regulation includes lists of emission-related 

maintenance and intervals for this maintenance. See 40 CFR 1039.125(a)(2) and 1039.125(a)(3). 

For example, in general, the maintenance interval for adjustment, cleaning, repair or replacement 

for catalytic converters on engines below 130 kilowatt (kW) may not occur more frequently than 

after 3,000 hours and 4,500 hours for engines at or above 130 kW. This regulation also includes 

a procedure that allows manufacturers to request a different maintenance schedule or to request 

new scheduled maintenance, which includes maintenance on emission-related components that 

were not in widespread use on NRCI engines prior to 2011. 

EPA adopted new emission standards applicable to emissions of NOX from light-duty 

vehicles and trucks on February 10, 2000 (65 FR 6698). Similarly EPA adopted new standards 

applicable to emissions of NOX from heavy-duty highway engines and vehicles on January 18, 

2001 (66 FR 5002). These standards have been phased in since model year 2004 and all were 

fully phased-in by 2010. Most manufacturers of affected diesel engines and vehicles have 

chosen to use a NOX reduction technology known as selective catalytic reduction (SCR) in order 

to meet these requirements. SCR systems use a nitrogen-containing reducing agent that usually 

contains urea and is known as diesel exhaust fluid (DEF). The DEF is injected into the exhaust 

gas and requires periodic replenishment by refilling the DEF tank. 

In addition, EPA adopted new emission standards applicable to emissions of NOX from 

NRCI engines on June 29, 2004 (69 FR 38958). These standards have begun to be implemented 

pursuant to a phase-in that began in the 2011 model year. EPA conducted a webinar workshop 

on July 26, 2011 with NRCI engine manufacturers to address the application of SCR emission 

technology. Some manufacturers are currently certifying their NRCI engines with the use of SCR 

systems and we expect that many manufacturers will use SCR systems to meet the final Tier IV 

NOX reduction requirements for their diesel engines. 

In a Guidance Document signed on March 27, 2007 (CISD-07-07), EPA indicated its 

belief that the requirements for critical emission-related maintenance would apply to 

replenishment of the DEF tank and that manufacturers wanting to use SCR technology would 

likely have to request a change to scheduled maintenance per 40 CFR §86.1834-01(b)(7) or 

§86.094-25(b)(7).
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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Following the completion of the Guidance, EPA received several requests for new 

maintenance intervals for SCR-equipped motor vehicles and motor vehicle engines.30 EPA 

granted these requests for model years 2009 through 2010 for light-duty vehicles and 2009 

through 2011 for heavy-duty engines, in a notice that was published in the Federal Register (74 

FR 57671, November 9, 2009). In granting the requests, EPA stated that it

believes the maintenance of performing DEF refills on SCR systems should be 

considered as ‘critical emission-related scheduled maintenance.’ EPA believes 

the existing allowable schedule maintenance mileage intervals applicable to 

catalytic converters are generally applicable to SCR systems which contain a 

catalyst, but that the DEF refills are a new type of maintenance uniquely 

associated with SCR systems. Therefore, the 100,000-mile interval at 40 CFR 

§86.1834-01(b)(4)(ii) for catalytic converters on diesel-cycle light-duty vehicles 

and light-duty trucks (and any other chassis-certified vehicles) and the 100,000-

mile interval (and 100,000 mile intervals thereafter) for light heavy-duty diesel 

engines and the 100,000-mile interval (and 150,000 mile intervals thereafter) for 

medium and heavy heavy-duty diesel engines at 40 CFR §86.004-25(b)(4)(iii) are 

generally applicable to SCR systems. As noted, the SCR systems are a new type 

of technology designed to meet the newest emission standards and the DEF refill 

intervals represent a new type of scheduled maintenance; therefore, EPA believes 

that manufacturers may request from EPA the ability to perform the new 

scheduled maintenance of DEF refills. 

EPA approved a maintenance interval for refill of DEF tanks equal to the applicable 

vehicle’s scheduled oil change interval for light-duty vehicles and light-duty trucks. For heavyduty engines, EPA approved a maintenance interval equal to the range (in miles or hours) of the 

vehicle operation that is no less than the vehicle’s fuel capacity (i.e., a 1:1 ratio), for vocational 

vehicles such as dump trucks, concrete mixers, refuse trucks and similar typically centrally 

fueled applications. For all other vehicles equipped with a constantly viewable DEF level 

indicator (e.g. a gauge or other mechanism on the dashboard that will notify the driver of the 

DEF fill level and the ability to warn the driver of the need to refill the DEF tank before other 

inducements occur), EPA approved a DEF tank refill interval equal to no less than twice the 

range of vehicle’s fuel capacity (i.e., a 2:1 ratio). For all other vehicles that do not have a 

constantly viewable DEF level indicator, EPA approved a DEF tank refill interval equal to no 

less than three times the range of the vehicle’s fuel capacity (i.e., a 3:1 ratio).

Engine and vehicle manufacturers provided additional requests for new maintenance 

intervals for vehicles and engines in model years not covered by the November 9, 2009 Federal 

 

30 See letter dated March 31, 2009 from Giedrius Ambrozaitis, Alliance of Automobile Manufacturers, Director, 

Environmental Affairs to Karl Simon, EPA, Director, Compliance and Innovative Strategies Division; Letter dated 

May 8, 2009 from Jed Mandel, Engine Manufacturers Ass’n to Karl Simon, EPA, Director, Compliance and 

Innovative Strategies Division; Letters dated June 29, 2009 and October 8, 2009 from Steven C. Berry, Director 

Government Relations Volvo Powertrain. 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

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Register notice.31 On January 5, 2012 (77 FR 488), EPA approved new maintenance intervals 

for the refill of DEF tanks applicable to light-duty vehicles and light-duty trucks, as well as for 

heavy-duty engines for 2011 and later model years. For light-duty vehicles and light-duty trucks 

the approved interval for DEF refill remains at the scheduled oil change interval. For heavy-duty 

engines the approved maintenance interval for vocational vehicles remains at 1:1 and for all 

other types of heavy-duty vehicles the approved maintenance interval is 2:1. 

On July 26, 2011, EPA conducted a webinar workshop for NRCI engine manufacturers in 

order to provide EPA’s thinking, at the time, about the certification of SCR-equipped NRCI 

engines. EPA discussed the issue of maintenance intervals for the refill of DEF and instructed 

manufacturers to follow the regulatory provisions in order to petition EPA for what it thought 

were appropriate intervals. Following the workshop, EPA received several requests for new 

maintenance intervals for SCR-equipped NRCI engines. EPA granted these requests for 2011 

and later model years in a notice that was published in the Federal Register (77 FR 497, January 

5, 2012). In granting the requests, EPA stated that it 

believes that SCR systems are a new technology and are properly considered a 

critical emission-related component. EPA believes the existing allowable 

schedule maintenance mileage intervals applicable to catalytic converters are 

generally applicable to SCR systems which contain a catalyst, but that the SCR 

systems are a new type of technology and that DEF refills are a new type of 

maintenance uniquely associated with SCR systems. Therefore, the 3,000 hour 

(engines below 130 kW) and 4,500 hour (engines at or above 130kW) intervals 

are generally applicable to SCR systems. As noted, the SCR systems are a new 

type of technology designed to meet the newest emission standards and the DEF 

refill intervals represent a new type of scheduled maintenance; therefore, EPA 

believes that manufacturers may request from EPA the ability to perform the new 

scheduled maintenance of DEF refills. 

EPA approved a maintenance interval for refill of DEF tanks that shall be no less than the 

equipment’s fuel capacity (i.e., a 1:1 ratio of DEF refill to fuel refill). 

B. Proposed Regulatory Action

EPA is today proposing to add DEF replenishment to the list of scheduled emissionrelated maintenance for diesel-fueled motor vehicles and motor vehicle engines, as well as for 

NRCI engines that use SCR. EPA is also proposing to incorporate appropriate maintenance 

intervals for this scheduled maintenance. 

 

31 See letter dated July 20, 2010 from Giedrius Ambrozaitis, Alliance of Automobile Manufacturers, Director, 

Environmental Affairs to Karl Simon, EPA, Director, Compliance and Innovative Strategies Division; Letter dated 

June 13, 2011 from Timothy A. French, Engine Manufacturers Ass’n to Justin G. Greuel, EPA, Compliance and 

Innovative Strategies Division; Letter dated April 28, 2011 from Steve Berry, Volvo Powertrain; Letters dated 

August 18, 2011 and September 27, 2011 to Karl Simon, EPA, Director, Compliance and Innovative Strategies 

Division from R. Latane Montague, Hogan Lovells. 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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(1) Scheduled Emission-Related Maintenance

EPA is proposing to list DEF replenishment as scheduled emission-related maintenance 

in 40 CFR 86.004-25(b)(4) and 40 CFR 86.1834-01(b)(4) for diesel-fueled motor vehicles and 

motor vehicle engines, as well as 40 CFR 1039.125(a)(2) and 40 CFR 1039.125(a)(3) for NRCI 

engines that use SCR.

Over the past several model years, since the implementation of the most recent standards 

for NOX, many manufacturers have chosen SCR as the technology used to meet these stringent 

NOX standards. Typically, should a manufacturer desire new maintenance (that it wishes to 

recommend to purchasers and perform during service accumulation on emission-data engines) 

not found in 40 CFR 86.004-25(b)(4) and 86.1834-01(b)(4) or at 40 CFR 1039.125(a)(2) and 40 

CFR 1039.125(a)(3), then it utilizes the provisions allowing manufacturers to request such 

maintenance. Given that SCR use is now common in the industry and replenishment of DEF is 

necessary for SCR to be effective, it is appropriate to add DEF replenishment to the list of 

scheduled emission-related maintenance published in the Code of Federal Regulations (CFR), 

rather than rely on the provisions of paragraph (b)(7) for motor vehicles and paragraph 

1039.125(a)(5) for NRCI engines. 

(2) Maintenance Intervals for On-Highway Diesel Engines

EPA is also proposing to incorporate appropriate maintenance intervals for this scheduled 

maintenance. In general, they are the same as were approved under the (b)(7) process. For lightduty vehicles and light-duty trucks, we are proposing an interval equal to the scheduled oil 

change interval for the vehicle. Light-duty vehicles and trucks do not have the carrying and 

storage capacity required for the quantity of DEF needed to satisfy longer maintenance intervals 

such as the 100,000 mile scheduled maintenance interval generally applicable to catalytic 

converters. As EPA explained in its previous notices regarding this issue, automobile 

manufacturers have stated that it takes approximately an 8 gallon DEF tank to assure the DEF 

will last for the length of a typical scheduled oil change interval. Assuming an oil change 

interval of 10,000 miles, a DEF tank size of approximately 80 gallons would be required to meet 

a 100,000 mile DEF refill maintenance interval. Even a 16-20 gallon DEF tank (to meet a 2 oil 

change interval) would interfere with the space that is necessary for typical light-duty vehicle 

design and transportation needs of the consumer. Interior cabin volume and cargo space are 

highly valued attributes in light-duty vehicles and trucks. Manufacturers have historically 

strived to optimize these attributes, even to the point of switching a vehicle from rear-wheel 

drive to front-wheel drive to gain the extra interior cabin space taken up by where the drive shaft 

tunnel existed, or switching the size of the spare tire from a conventional sized tire to a small 

temporary tire to gain additional trunk space. Thus any significant interior, cargo or trunk space 

used to store a DEF tank would be unacceptable to customers. There are also packaging 

concerns with placing a large DEF tank in the engine compartment or in the vehicle’s 

undercarriage. Most vehicle undercarriages are already crowded with the engine, exhaust 

system, including catalytic converters and mufflers, fuel tank, etc. limiting any available space 

for a DEF tank. 

 In addition to the inherently space constrained areas on the vehicle to place both fuel 

tanks and DEF tanks (an additional 8 gallon tank represents a very significant demand for space) 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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the addition of the weight associated with the DEF represents significant concerns (e.g. 

performance and efficiency) on the operation of the vehicle. For example, assuming a density of 

9 lb/gallon, an 8 gallon DEF tank represents an additional 72 lbs on a vehicle already looking to 

optimize performance. Adding additional DEF tank size to even accommodate a two-oil change 

interval is not feasible or practical given these weight constraints. A requirement for a larger 

DEF tank may also have an adverse effect on the ability of a manufacturer to meet greenhouse 

gas emission standards and fuel economy standards. 

EPA notes that a DEF refill maintenance interval that is equivalent and occurring with the 

oil change interval is a fairly long interval (e.g. 7,500 to 12,500 miles) for light-duty vehicles and 

trucks and is not likely to result in overly frequent maintenance under typical vehicle driving. 

EPA also believes that an adequate DEF supply will be available to perform the DEF refills at 

the stated intervals. EPA believes it important to also consider when, where and how often 

vehicle owners or operators are most likely to perform the DEF refill maintenance. For lightduty vehicles and light-duty trucks, EPA believes the requested DEF refill interval’s association 

with the oil change interval is appropriate given the likelihood of DEF availability at service 

stations and the likelihood that DEF refill would occur during such service. 

EPA also notes that heavy-duty engines that are certified as part of complete trucks have 

been treated in the same manner as light-duty trucks and thus have been subject to the DEF refill 

interval associated with the oil change. We are proposing to continue this treatment in the 

regulations. In addition, EPA is aware that several manufacturers are exploring whether the DEF 

refill interval should not be linked to the oil change interval since the historical oil change 

interval (e.g., 7,000-8,500 miles) is potentially increasing to higher mile intervals (e.g., 15,000 to 

30,000 miles, even higher for synthetic oil). We invite comment on the necessity and 

appropriateness of “de-linking” the DEF refill interval from the oil change interval, as well as 

comments on proper methods to increase the likelihood that DEF refill maintenance would occur 

in the appropriate interval (e.g., linking to vehicle fuel capacity, inducement criteria, etc.), should 

it not be linked to the oil change interval.

For heavy-duty engines, we are proposing that for vocational vehicles such as dump 

trucks, concrete mixers, refuse trucks and similar typically centrally fueled applications, the DEF 

tank refill interval should equal the range (in miles or hours) of the vehicle operation that is no 

less than the vehicle’s fuel capacity (i.e., a 1:1 ratio). For all other vehicles, the DEF tank refill 

interval must provide a range of vehicle operation that is no less than twice the range of vehicle’s 

fuel capacity (i.e., a 2:1 ratio). EPA believes it is reasonable to base the DEF refilling event on 

diesel refueling intervals given that it is likely that the DEF refill maintenance would be 

undertaken at the time of fuel refill due to DEF infrastructure developed at diesel refueling 

stations. EPA believes that these DEF refilling intervals are technologically necessary. EPA 

knows of no SCR technology for any heavy-duty engine application that is capable of operating 

without a DEF refill for the high mileage levels associated with other maintenance intervals. As 

an example, assuming that 25,000 gallons of diesel fuel were consumed to reach a 150,000 mile 

interval, the amount of DEF required (assuming a 3% DEF consumption rate) would require 750 

gallons of DEF weighing approximately 6,750 lbs. A line-haul truck is allowed a maximum 

gross vehicle weight of 85,000 lbs. of which approximately 45,000 pounds is for cargo carrying. 

A DEF tank of 750 gallons would reduce the cargo-carrying capacity by 15%. Another example 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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from the line haul industry suggests that a DEF tank size of over 900 gallons would be needed to 

reach the 150,000 mile interval for a common highway vehicle with a diesel fuel capacity of 200 

gallons and achieving 6.5 miles per gallon fuel economy. Similarly, a medium heavy-duty 

engine (“chassis cabs”) example would require 375 gallons of DEF weighing 3,275 lbs to meet a 

150,000 mile interval. EPA believes that such tank sizes are clearly not technologically feasible 

in light of the weight and space demands and constraints on heavy-duty trucks and the consumer 

demand to maximize cargo carrying capacity.

The Agency also believes that intervals shorter than 150,000 miles but longer than those 

we are proposing would require DEF tanks that are too large or too heavy to be feasibly 

incorporated into vehicles. Available data show that heavy-duty engines equipped with SCRbased systems will consume DEF at a rate that is approximately 2%-4% of the rate of diesel fuel 

consumption. Because of inherent space and weight constraints in the configuration and efficient 

operation of heavy-duty vehicles, there are size limits on the DEF tanks. Currently, there are 

truck weight limits that manufacturers must address when making or modifying truck designs. 

EPA expects and believes that manufacturers are taking significant and appropriate steps in order 

to install reasonably sized DEF tanks to achieve the DEF refills intervals noted. For example, 

manufacturers are taking such steps as reducing the number of battery packs on vehicles despite 

customer demands or designing space saving configurations, in some instances extending an 

already very limited frame rail distance to incorporate the DEF tanks and SCR systems, moving 

compressed air tanks inside the frame rails, redesigning fuel tank configurations at significant 

costs, and otherwise working with significant size and weight constraints to incorporate DEF 

tanks. There are several factors that support the good engineering judgment that underlies the 

recommended DEF refill intervals. The great majority of heavy-duty engines produced with 

SCR DEF tanks will provide a range of vehicle operation that is no less than twice the range of 

the vehicle’s fuel capacity; thus, the DEF tank size will provide at least double the vehicle’s 

operating range as provided by the fuel tank. Vehicle operators will generally refill DEF at the 

same time and location that they refill the tanks thus these vehicles will already be carrying twice 

as much DEF as the SCR system could ever consume between refills. Also, manufacturers have 

been incorporating warning signals and performance-related inducements on their SCR-equipped 

vehicles to ensure the substantial likelihood that DEF refilling will occur,32 and there is 

considerable evidence that heavy-duty vehicle operators in the United States have in practice 

been refilling their DEF tanks prior to the tanks becoming empty in virtually all situations.33 

EPA was provided with examples of the consequences of requiring heavy-duty vehicles 

to accommodate a DEF refill interval of 5:1, and the information provided to the Agency 

strongly suggested that great compromises would be required in cost, weight and utility. 

Increased tank sizes and weights on the magnitude of 150 to 325 lbs. would be required and in 

some cases diesel fuel volumes would need to be reduced. The extra weight associated with the 

DEF required to meet the 2:1 refill intervals represents a significant challenge to manufacturers 

 

32 As discussed in Section IV above, we are proposing options for manufacturers of emergency vehicles and engines 

to avoid the harsh consequences of certain performance inducements. Since 2010, some manufacturers have been 

implementing guidance on alternative inducement criteria for emergency vehicles.

33 See 76 FR 32886 (June 7, 2011) and the studies cited at 32889-32891. 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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seeking to meet both weight and size requirements for their vehicle designs. In addition, 

requiring a longer DEF refill interval may result in increased greenhouse gases and decreased 

fuel economy. EPA believes that in light of the existing tight space constraints and the overall 

desire to maximize cargo-carrying capacity to minimize emissions and meet consumer 

operational demands, and the built-in DEF tank size buffer to insure DEF refills, that the 

proposed tank DEF tank sizes are technologically necessary and are also reasonable and 

appropriate. EPA believes that requiring tank sizes above these ratios will cause increases in 

space constraints and weight that would not be appropriate for these vehicles. Similarly, 

manufacturers note that only a small number of applications will employ the 1:1 refilling ratio 

and that such vehicle applications have very limited vehicle space available to house surplus 

DEF. Such applications (e.g., a garbage truck, concrete mixer, beverage truck, or airport 

refueler) will also be refueled daily at central locations. At approximately 0.134 ft3

 per gallon, 

any extra DEF would displace significant space available to vehicle components and subsystems 

on both the vocational trucks at the 1:1 refill interval as well as the 2:1 vehicles.

During the previous administrative process leading to the January 5, 2012 Federal 

Register notice approving new maintenance intervals, EPA received a comment from one 

manufacturer (Navistar) suggesting that a longer DEF refill interval in the range of 35,000 to 

45,000 miles was appropriate. EPA responded to these comments in detail in that notice.34 As 

discussed in that notice, Navistar claimed that other technology is available that would need a 

maintenance interval no shorter than this. However, EPA found no evidence that such 

technology is actually available at this time. More importantly, the fact that other technology 

may be able to have a longer maintenance interval does not mean that a longer maintenance 

interval is appropriate for DEF-based SCR. Navistar suggested that maintenance intervals can be 

increased by doubling DEF tank size. EPA does not believe that requiring such an increase is 

appropriate given the numerous negative consequences discussed above. EPA also explained 

that Navistar’s suggestion of reducing engine-out emissions of NOX would likely lead to an 

increase in fuel consumption, and possible increases in GHG emissions, and could either require 

increases in the size of the fuel tank or more reductions in the operating range of a vehicle before 

needing to refill, which would compromise a critical design parameter of heavy-duty vehicles. 

EPA does not believe the desire to increase DEF maintenance intervals justifies such 

consequences. After reviewing these data, EPA believes that longer refill intervals than those 

proposed above would require larger and heavier DEF tanks. The design and engineering work 

performed by manufacturers thus far indicates that the recommended DEF refill intervals noted 

above approximate the maximum feasible maintenance intervals associated with reasonable DEF 

tank sizes. In any case these refill intervals are appropriate and reasonable given the substantial 

negative consequences of longer DEF refill interval requirements. The recommended 

maintenance intervals ensure that the function and operational efficiency of such vehicles are not 

overly compromised. Based on this information we believe the proposed intervals are warranted. 

EPA has received comments from certain manufacturers indicating that EPA should set 

the minimum required DEF refill interval at an interval equal to the vehicle’s fuel capacity (i.e., a 

 

34 See 77 FR 488, at 495-96 (January 5, 2012).
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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1:1 ratio) for all heavy-duty engines.35 The commenters claim that this shorter maintenance 

interval is “necessary and appropriate to reflect current and anticipated changes in vehicle 

designs, significant changes in inducement strategies, and the increased availability of DEF.” 

The commenters note that certification practices of the EPA regarding inducement practices for 

SCR-equipped engines make it “essentially impossible for an SCR vehicle to operate without 

regular DEF replenishment.” They state that the severity of inducements related to DEF levels

(e.g. severe reduction in engine power and/or vehicle speed) is “extraordinary and must be taken 

into account” when EPA is determining appropriate maintenance intervals. They state that “in 

light of these severe inducements, it is reasonable to expect that a driver with a 1:1 tank ratio will 

operate under a firm discipline that the DEF tank must be refilled every time the fuel tanks are 

filled, as opposed to a driver with a 2:1 or greater tank ratio who may become accustomed to 

filling the DEF tank only when necessary, and is therefore more likely to rely on gauge levels, 

warnings, and inducements to trigger refills.” 

The commenters also state that EPA’s promulgation of new standards regulating 

greenhouse gases increase the size and weight restraints associated with DEF tank size. 

EPA has adopted new greenhouse gas standards for heavy-duty on-highway trucks, and 

manufacturers have moved to voluntarily increase the fuel efficiency of their vehicles in advance 

of the effective dates of those regulations. Within these regulations, EPA recognizes the impact 

of weight savings on fuel efficiency and GHG emissions. In addition, manufacturers have 

developed innovative new DEF dosing strategies to reduce CO2 emissions. These new strategies 

may involve increasing the DEF dosing rate. Increasing the DEF dosing rate also makes it more 

difficult to satisfy a 2:1 tank size ratio without increasing the size of the DEF tank above the size 

EPA previously considered the maximum reasonable size. For this reason, if the application of 

the 1:1 tank ratio is not expanded, EPA will effectively be mandating larger DEF tanks, with 

their accompanying weight increase, in order to accommodate technology advancements 

developed to reduce CO2 emissions—tanks that are larger than the tanks EPA determined to be 

the maximum reasonably required in 2009. In addition, this could inadvertently cause 

manufacturers to restrict application of the most fuel efficient engines to vehicles that have 

reduced range between fuel and DEF refills, such that they will be unattractive to the line-haul 

fleets that consume the most fuel. 

The commenters elaborated that: 

To meet the next round of GHG reduction requirements, some manufacturers 

expect to increase DEF dosing by as much as 100% over current levels. These 

increased levels of dosing will require a corresponding increase in DEF tank 

capacity and size to meet the existing 2:1 tank ratio requirements. For example, 

increasing DEF dosing by 40% on average would require an increase in DEF tank 

size of approximately 40% (depending on how much extra capacity was included 

in the tanks used in previous model years). The shape, size and location of DEF 

 

35 See letters dated August 18, 2011 and September 27, 2011 to Karl Simon, EPA, Director, Compliance and 

Innovative Strategies Division from R. Latane Montague and Hogan Lovells. 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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tanks on a truck frame are constrained by a number of factors including: the need 

to place the tank below the filler-neck; the need for clearance from other 

components such as fuel tanks, battery boxes, air tanks, diesel particulate filters, 

and the drive axle and wheels; the need for gravity feed; body installation 

requirements; clear-back-of-cab requirements; weight distribution requirements; 

bridge formula and related axle placement issues; and fuel capacity/driving range 

demands. 

The commenters state that another consequence of the greenhouse gas regulations is more 

attention to improved aerodynamics and weight reduction, which are harmed by the need for a 

2:1 DEF tank size requirement. They claim that EPA should allow manufacturers to use all 

available options to increase fuel efficiency and meet greenhouse gas standards. They claim that 

the possible harm of allowing shorter maintenance intervals are minimal, given the severe 

negative inducements associated with failure to replenish the DEF tank. 

EPA is not proposing to allow a 1:1 DEF maintenance interval across the heavy-duty 

engine class at this time. EPA notes that manufacturers have been meeting a 2:1 ratio for DEF 

tank size for the past two years and the commenters have not provided sufficient evidence that 

this ratio will be infeasible in the future. Moreover, the commenters have not shown that any 

change in the maintenance interval is necessary or appropriate throughout the heavy-duty engine 

category, rather than for particular applications, or that a refill interval as low as 1:1, rather than 

1.8:1 or 1.5:1, is necessary or appropriate. The feasibility of the greenhouse gas standards was 

not predicated on substantial increases in DEF dosing rate, although that was a possible method 

of compliance, and the commenters have not shown that the increase in tank size that would be 

associated with increased dosing, which need not be large, would be inconsistent with space 

constraints. While EPA agrees that the warnings and inducements in place for failure to 

replenish DEF will restrict the ability of operators to run without DEF, and have made operation 

without DEF virtually unheard of, a DEF tank ratio of 1:1 greatly increases the likelihood that 

operators will need to make more frequent stops to replenish DEF, and possibly may need to stop 

solely to replenish DEF, which may place a greater burden on the operator in terms of the 

frequency of DEF refills. However, we request comment on this proposal and we do not rule out 

the possibility we may in the final rule allow a shorter maintenance interval at least in some 

situations beyond what we have proposed. In particular, we request comment on whether such 

an interval may be appropriate in the future or whether an approach that is limited to a portion of 

the heavy-duty engine category or that uses an interval between 2:1 and 1:1 may be appropriate. 

EPA also notes that the regulations allow any manufacturer to petition EPA under the 

“paragraph (b)(7) process” for a shorter maintenance interval than that promulgated for DEF 

refills if the manufacturer can show that a shorter interval is technologically necessary for the 

particular engine or vehicle configuration being certified. 

(3) Maintenance Intervals for Nonroad Compression-Ignition Engines

EPA is also proposing to incorporate appropriate maintenance intervals for the scheduled 

maintenance of DEF refills on SCR-equipped NRCI engines. We are proposing the same 

interval (i.e., 1:1 ratio) as was approved under the § 1039.125(a)(5) process. 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

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EPA believes it appropriate to evaluate the DEF refill rates by taking into consideration 

the space and weight constraints typically involved with the range of nonroad compressionignition engines using SCR systems, including safety and impacts of weight and dosing rates on 

greenhouse gas emissions and fuel economy. EPA also believes it appropriate to take into 

consideration the likelihood that the maintenance of DEF refills will be performed by the owner 

or operator.36 

EPA knows of no SCR technology for NRCI engines that is yet capable of attaining 

longer operation (generally beyond one tank full of diesel) without a DEF refill. As noted by the 

requests received for a shorter interval, there are significant space and weight constraints 

associated with increasing the DEF tank size in order to accommodate a 2:1 refill ratio. EPA 

believes it appropriate to take into consideration the need for locating the DEF tank in close 

proximity to the fuel tank and the remainder of the SCR system, as well as the increased 

likelihood that the DEF tank will be refilled if it becomes standard operating practice to refill it 

at the same time as the fuel tank. EPA believes that such nonroad equipment is similar to 

centrally-fueled heavy-duty on-highway vehicles and that there is a sufficient basis and a 

reasonable expectation that DEF tank refills will occur on a timely basis. In addition, because 

this maintenance is considered critical emission-related maintenance, § 1039.125 requires that 

manufacturers ensure that it have a reasonable likelihood of being done at the recommended 

intervals on in-use engines. Paragraph 1039.125(a)(1) sets forth several methods by which such 

demonstration can be made, including data showing that if a lack of maintenance increases 

emissions, it also unacceptably degrades the engine’s performance. Thus, manufacturers will 

need to show compliance with this requirement to be certified. In the context of SCR systems 

and the potential of an empty DEF tank and an inoperable SCR system, EPA notes that 

equipment under such operating conditions are expected to shut down or idle only.37 

VI. Nonroad Engines in Temporary Emergency Service

As noted previously, EPA is proposing to adopt special provisions for engines used in 

dedicated emergency vehicles to ensure that manufacturers are able to design and implement 

reliable, robust emission control systems with regeneration strategies that do not interfere with 

the mission of emergency vehicles. However, we are not proposing to extend this option for 

other engines that are not intended for emergency vehicles. Nevertheless, based on information 

provided to us from engine manufacturers, we have some concern that nonroad engines not 

normally used for emergencies may be needed in unusual emergency situations that may require 

very limited and temporary relief so that emission controls do not hinder the engine’s 

performance in such emergency conditions. This section describes a flexibility that we are 

proposing to address this. 

Our existing nonroad engine compliance regulations in 40 CFR 1068.101(b)(1)(ii) allow 

operators to temporarily disable or remove emission controls to address emergency situations. 

 

36 See 40 CFR 1039.125(a)(5). 37 See 76 FR 32886 (June 7, 2011) and related inducement criteria, see also Note 32 above regarding inducements 

for emergency vehicles and engines.
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However, they do not necessarily allow manufacturers to design the emission controls to be 

disabled or removed. This has become a potential problem for modern electronically controlled 

engines, where many emission controls are integrated into the engine’s control software. There 

is currently no way for an operator to selectively disable emission control software, while 

maintaining engine function. The proposed regulatory text would effectively extend the policy 

expressed in 40 CFR 1068.101(b)(1)(ii) to emission control software.

A. Use of Nonroad Engines in Emergency Situations

The provisions we are proposing are intended primarily to address engines used for 

power generation or in construction equipment. However, it is important to note that we are not 

proposing to limit this flexibility to such engines. For example, portable diesel-powered 

generators are often used to provide electrical power after natural disasters. If the generator is 

providing power to a medical facility, then any interruption in service could risk the lives of the 

patients. This is just one example of how an ordinary piece of nonroad equipment could be used 

in an emergency situation. Others would include bulldozers repairing a levee or a crane 

removing debris. 

The Tier 4 standards have resulted in much of this equipment being equipped with SCR 

catalysts that require a reductant. The reductant is typically supplied as a urea water solution 

known as diesel exhaust fluid (DEF). The engines in this equipment generally include controls 

that limit the function of the engines if they are operated without urea. Such controls are 

generally call “inducements”, because they induce the operator to supply urea to the equipment. 

While we are confident that DEF is now widely and easily available in the United States, we are 

concerned that in emergency circumstances there may be a possibility of a temporary supply 

shortage. We believe that in such situations, temporary flexibilities may be appropriate because 

the possibility of risk to human life sufficiently outweighs the temporary emissions increases that 

may occur if SCR-equipped engines are used without DEF. As indicated below, this flexibility is 

very narrow and contains several provisions to ensure the need for the relief. We do not believe 

it can or will be used in situations where there is no critical need for such relief. 

B. Proposed Regulatory Action

(1) General Requirements

We are proposing a new section 1039.665 that would specify provisions that allow for 

AECD’s that are necessary to ensure proper function of engines and equipment in emergency 

situations. AECD’s approved under this section would not be defeat devices. The section would 

include the following provisions: 

• Manufacturers would be allowed to ask for approval at any time. Still, we would encourage 

manufacturers to obtain preliminary approval before submitting an application for 

certification. And in unusual circumstances, we could allow manufacturers to apply an 

approved emergency AECD to engines and equipment that have already been placed into 

service as a “field fix”.
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• The manufacturer would be required to keep records to document requests for and use of 

emergency AECD’s under this section and submit a report to EPA within 60 days of the end 

of each calendar year in which it authorizes use of the AECD

• We would approve an AECD only where we determine certain criteria are met, as described 

below. 

We are proposing to address such AECD’s as part of certification and would only 

authorize the certifying manufacturer to activate them.

(2) Approval Criteria

Approval of AECD’s under the proposed regulations would be based on certain general 

and specific criteria. A general criterion is that the AECD would need to be consistent with good 

engineering judgment. When used in our regulations, the phrase “good engineering judgment” 

has a specific meaning as described in 40 CFR 1068.5. By specifying that the AECD be 

consistent with good engineering judgment, we address unforeseen technical details that may 

arise.

We are also proposing three specific criteria that must be met. Each of these criteria is 

intended to ensure that any adverse environmental impacts are minimized. These criteria are:

• The AECD must be designed so that it cannot be activated without the specific permission of 

the certificate holder. We would specify that the AECD must require the input of a 

temporary code or equivalent security feature.

• The AECD must become inactive within 24 engine hours of becoming active (or other period 

we approve in unusual circumstances). 

• The manufacturer must show that the AECD deactivate emission controls (such as 

inducement strategies) only to the extent necessary to address the expected emergency 

situation. 

(3) Allowable Use of Emergency AECD’s 

This allowance is intended generally to address SCR-equipped engines operating in 

emergency situations when DEF is unavailable. In such cases, inducement strategies could result 

in a loss of power of the engine which could effectively prevent the equipment from functioning. 

Under this provision, a manufacturer could include a dormant feature in the engine’s control 

software that could be activated to disable inducement strategies.

We are also proposing to allow this for other types of controls, where a manufacturer can 

clearly demonstrate that this relief could be needed. We are requesting comment about whether 

we should specifically identify such other controls or leave the regulatory text more open ended. 

Finally, we are requesting comment about the circumstances under which we should 

allow the AECD to be activated. Should emergency situations include only those circumstances 

where human life is at stake? Should it be allowed automatically whenever a federal disaster is 

declared? 
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VII. Economic, Environmental, and Health Impacts of Proposed 

Rule 

A. Economic Impacts

(1) Economic Impacts of Emergency Vehicle Proposal

EPA expects the economic effects of this proposal to be small, and to potentially have 

benefits that are a natural result of easing constraints.

(a) Costs to Manufacturers 

Due to the optional and voluntary nature of this proposal, there are no direct regulatory 

compliance costs to engine manufacturers. To the extent manufacturers elect to develop and 

deploy upgrades to engines for emergency vehicles, they may voluntarily incur some degree of 

costs associated with the following:

• Design and testing to determine effectiveness of potential AECD’s

• Education & outreach to intermediate vehicle manufacturers and end users 

• Deployment of AECD’s onto new and in-use emergency vehicles

• Labeling costs

EPA expects any fixed costs would be small, and any variable costs would apply only to 

the engines sold for installation in emergency vehicles or emergency equipment, which comprise 

less than one percent of the heavy-duty on-road fleet, and an even smaller fraction of the nonroad 

fleet. As per standard practice, manufacturers would be free to set a fair market price for any 

approved AECD or field modification they offer, to offset the costs incurred in its development. 

(b) Operational Costs 

Depending on the type of AECD or field modification that a manufacturer voluntarily 

elects to deploy, some operational costs could increase and some could decrease.

(i) Maintenance and Warranty Costs 

When an emergency vehicle is experiencing frequent plugging of its DPF, this increases 

maintenance costs for owners and warranty costs for manufacturers. Maintenance costs can 

include service calls for a technician-controlled regeneration, towing fees where on-site 

regeneration cannot be achieved, and costs to deploy reserve vehicles while the impaired vehicle 

is being serviced. These costs are expected to decrease with this proposal, and are discussed 

further below. 

Manufacturers incur warranty costs when a vehicle under warranty must be returned for 

service. Because this proposed action would allow manufacturers the flexibility to improve the 

reliability of their engines, EPA expects warranty costs for emergency vehicles and engines in 

emergency vehicles would decrease as a result of this action.
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Should an AECD be deployed that allows manual active regenerations at more frequent 

intervals, this could increase the total number of regenerations, exposing the DPF substrate to 

more frequent thermal stress and general wear & tear. However, while it is expected that the 

frequency of regenerations would increase, the duration of each regeneration would decrease 

because the total soot loading of the DPF would likely remain unchanged or be reduced due to 

other control strategies within the approved AECD. Because manufacturers are held to strict 

standards related to the warranty, maintenance and durability of these systems, EPA expects that 

measures will be taken to ensure that any AECD that is deployed would not decrease the ash 

cleaning interval or otherwise decrease the durability of the emission control system.38

With this proposal, manufacturers would have the flexibility to design alternate 

calibrations to reduce soot loading to the DPF and extend the interval between regenerations. 

There would also be more flexibility to enable more passive and automatic active regenerations, 

which both expose the DPF to less thermal stress than do manual active regenerations. In 

summary, EPA does not expect any warranty or maintenance costs would increase due to this 

proposal, and it is very likely that these would decrease. Furthermore, EPA believes that the 

potential for reduced warranty costs may help to offset the cost to produce and deploy any 

optional AECD’s. Similarly, EPA believes the potential for reduced maintenance and 

operational costs may offset the cost to owners for obtaining requested AECD’s. 

(ii) Fuel Costs from Dosing 

Where DPF systems employ fuel dosing to enable active automatic regenerations, it is 

uncertain whether liberalizing the parameters for initiating regenerations would affect fuel 

consumption. Operators have reported that vehicles burn more fuel during regenerations, though 

the quantity varies among vehicles. 

Where automatic active regenerations employ fuel dosing, it is uncertain whether fuel 

consumption would increase with an increased number of regenerations during a given operating 

period. If all else were to remain the same, it is likely that the duration of each automatic active 

regeneration may be decreased. To the extent regenerations are enabled with other means 

besides fuel, or demand for regenerations is reduced through recalibration, then any potential 

increase in fuel use from dosing would be mitigated. 

As an illustration, we have estimated the additional fuel use for a truck with a dosing 

strategy where its regeneration interval is decreased from 25 hours to eight hours, due to the 

increased availability of operator-commanded regenerations. In this example, we assume a 

single regeneration consumes approximately half a gallon of supplemental fuel. If the vehicle has 

average engine operating hours of 1,200 per year, then its number of regeneration events would 

increase from about 50 per year to 150 per year, under the above assumptions. If the amount of 

supplemental fuel use remained unchanged under the new regime (a conservative assumption) 

then potentially the vehicle could consume an additional 50 gallons of fuel per year from the 

 

38 EPA prohibits engine manufacturers from requiring repair or replacement of particulate traps on heavy heavy-duty 

diesel engines more than once every 150,000 miles. 40 CFR 86.004-25(b)(4)(iii).
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increased frequency of regenerations alone. Considering current costs of ultra low sulfur diesel 

fuel, this could translate to about $200 per vehicle in additional annual fuel costs. 

As explained above, EPA does not believe this is a likely scenario, as the amount of fuel 

used per regeneration event would likely decrease with increasing frequency, and engine 

manufacturers would be likely to adjust combustion parameters to avoid placing additional 

thermal stress on the DPF. A more detailed analysis of fuel use and potential costs associated 

with dosing strategies is included in a memo to the docket associated with this rulemaking.39

(c) Societal Costs 

Because this proposal eases constraints on the development of robust DPF systems, the 

economic impacts can only improve with this action. It is presumed that the benefits to society 

of enabling first responders to act quickly when needed outweigh the costs to society of any 

temporary increase in emissions from this small segment of vehicles.

(2) Economic impacts of SCR Maintenance Proposal 

This action would codify previously published final agency actions regarding SCR 

maintenance intervals. No new regulatory burdens would be imposed. Rather, by codifying 

former decisions that were based on administrative petitions and of limited applicability, EPA is 

providing regulatory certainty that will allow affected manufacturers to plan their product 

development accordingly. 

(3) Economic Impacts for Nonroad Engines Used in Emergency Situations

EPA expects the economic effects of this proposal to be small, and to potentially have 

benefits that are a natural result of easing constraints. Due to the optional and voluntary nature 

of this proposal, there are no direct regulatory compliance costs to engine manufacturers. To the 

extent manufacturers elect to develop and deploy upgrades to engines for emergency vehicles, 

they may voluntarily incur some degree of costs. We do not expect there to be any operator 

costs for this allowance, other than the potential cost associated with sending written 

confirmation of an emergency situation to the certificate holder. However, since this option 

would be activated rarely (or perhaps not at all), total costs to operators would be negligible. 

B. Environmental Impacts

(1) Environmental Impacts of Emergency Vehicle Proposal

We expect any environmental impacts from this proposal would be small. By 

promulgating these amendments, it is expected that the emissions from this segment of the 

heavy-duty fleet would not change significantly. 

 

39 See memo dated May 4, 2012, “Fuel Use With Dosing for DPF Regeneration,” Docket ID EPA-HQ-OAR-2011-

1032. 
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(a) Fleet Characterization and Emission Inventory 

EPA estimates that on-road emergency vehicles comprise less than one percent of the 

national heavy-duty fleet. According to the International Council on Clean Transportation 

(ICCT), less than one percent of all new heavy-duty truck registrations in 2003 to 2007 were for 

emergency vehicles (includes class 8 fire trucks plus other class 3-8 emergency vehicles).40 On 

average, the ICCT’s data suggest that approximately 5,700 new emergency vehicles are sold in 

the U.S. each year; about 0.8 percent of the 3.4 million new heavy-duty trucks registered 

between 2003 and 2007. The available information indicates that the emergency vehicles 

included in the scope of this rulemaking have lower annual vehicle miles traveled than average 

non-emergency vehicles. Therefore, we conclude that they contribute less than 1% of the annual 

air emissions from the heavy-duty diesel truck fleet. 

(b) Emission Impacts from Auxiliary Emission Control Devices on Emergency Vehicles

Due to the optional and voluntary nature of this action, it is difficult to estimate its overall 

emissions impact accurately. The proposed amendments offer many options to manufacturers, 

and the emissions impacts will depend on which options and strategies are employed, and for 

how many vehicles.

(i) NOX Emissions Impacts 

During both automatic active and manual active regenerations, emission rates increase for 

some pollutants, especially NOX when post-DPF after-treatment devices are not present. The 

higher than normal combustion chamber temperatures during active regeneration with high rates 

of oxidation occurring across the catalyst can create conditions conducive to NOX formation. 

From certification data for 2008 model year engines, the difference between the NOX emission 

rate during normal operation and the rate during active regeneration can range from an 

undetectably small difference to a five-fold increase. The magnitude of the NOX increase is only 

part of the story, however. As part of their certifications, engine manufacturers may provide 

frequency factors that adjust for the average excess emissions during DPF regeneration. As used 

in engine certification, the frequency factor indicates the percent of test cycles during which DPF 

regeneration is expected to occur. From certification data for 2008 and 2011 model year 

engines, DPF regeneration frequency factors for heavy-duty engines range from near zero to 

nearly 20 percent. Overall, the certification data indicate that the higher the increase in NOX

during a DPF regeneration event, the less often active regeneration occurs on that engine, 

especially over the transient test cycle. A summary of this information is presented in a memo to 

the docket associated with this rulemaking.41

 As a result of this proposed action, it is possible that some engine manufacturers will 

submit applications for AECD’s with liberalized parameters under which automatic active and/or 

 

40 ICCT, May 2009, “Heavy-Duty Vehicle Market Analysis: Vehicle Characteristics & Fuel Use, Manufacturer 

Market Shares.” 41 See memo dated May 4, 2012, “NOX Emissions from DPF Regeneration,” Docket ID EPA-HQ-OAR-2011-1032. 
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manual active regenerations may occur, for emergency vehicles. Under these liberalized 

parameters, several outcomes are possible, depending on the engineering design. While the NOX

emission rate during DPF regeneration could increase above the rate of the current certified 

configuration, it is also possible that the duration of each event could decrease. While the 

frequency of manual active regenerations could increase if the engine controls permitted 

operators to initiate parked regeneration at any soot loading, it is also possible the frequency of 

automatic or manual active regenerations could decrease with the new designs, making wider use 

of passive regeneration strategies. Given that it is difficult to estimate how popular each option 

may be, and what other actions may be taken to alter engines and/or emission control systems, 

EPA has provided examples of possible emission scenarios due to this proposal in a memo to the 

docket.42

(ii) PM emissions Impacts 

In the comment letters EPA received urging swift action providing relief for emergency 

vehicles, it was often cited that the pollution from a structural fire is far worse than the tailpipe 

emissions of a fire truck. To provide some perspective on this, EPA is providing a brief 

discussion of PM emissions in this section. 

A rough method for estimating emissions from structural fires is obtained by multiplying 

a national average factor of 2.3 fires per 1,000 residents by the national population, along with a 

PM emission factor of 10.8 lb per ton burned, and an average fuel loading of 1.1 tons burned per 

fire. Using these estimates, EPA calculates just under 5,000 tons of PM is emitted in the U.S. 

each year from structural fires. A more detailed analysis of PM emissions from structural fires in 

relation to PM emissions from emergency vehicles is included in a memo to the docket 

associated with this rulemaking.43

We expect manufacturers who choose to develop optional AECD’s for emergency 

vehicles to employ strategies that prevent the occurrence of abnormal conditions of the emission 

control system. Where preventive strategies alone are not demonstrated to be failsafe, EPA 

expects there may be instances where it is justified to provide engine exhaust backpressure relief, 

either mechanical or through other means. While we expect this will not be a widespread 

solution, there may be cases where a relief valve may be employed on a vehicle whose DPF 

became plugged frequently, allowing temporary emission control bypass to occur as a last resort 

to prevent engine failure. An example of possible PM emissions changes due to this proposal is 

presented in a memo to the docket associated with this rulemaking.44

(iii) Fuel Use from Dosing 

As described above in Section IV.C, only some control systems employ fuel dosing as a 

strategy to initiate active regeneration. In a memo to the docket associated with this rulemaking, 

 

42 See NOX Memo, Note 41, above. 43 See memo dated May 4, 2012, “PM Emissions Impacts,” Docket ID EPA-HQ-OAR-2011-1032 44 See PM memo, Note 43, above. 
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EPA estimates the potential increase in fuel use due to more frequent operator-commanded 

regenerations with dosing at an average of about 50 gallons per year per vehicle, if other 

measures to reduce the need for regenerations are not taken.45 The emissions associated with 

this supplemental fuel use are discussed above. EPA requests comment on the impact of this 

proposed action on fuel consumption in emergency vehicles whose active regeneration strategies 

include fuel dosing. 

(2) Environmental Impacts of SCR Maintenance Proposal 

EPA believes that the likelihood of emissions-related maintenance occurring in use 

would remain unchanged as a result of this action. Therefore, there are no anticipated adverse 

environmental impacts.

(3) Environmental Impacts for Nonroad Engines Used in Emergency Situations

EPA does not expect any significant environmental effects as a result this proposal. This 

option would be activated rarely (or perhaps not at all) and would only affect emissions for a 

very short period. 

C. Health Effects

EPA’s clean diesel standards are already providing substantial benefits to public health

and welfare and the environment through significant reductions in emissions of NOX, PM, 

nonmethane hydrocarbons (NMHC), carbon monoxide, sulfur oxides (SOX), and air toxics. We 

project that by 2030, the on-highway program alone will reduce annual emissions of NOX, 

NMHC, and PM by 2.6 million, 115,000 and 109,000 tons, respectively. These emission 

reductions will prevent 8,300 premature deaths, over 9,500 hospitalizations, and 1.5 million 

work days lost. All told, the monetized benefits of the on-highway rule plus the nonroad diesel 

Tier 4 rule total over $150 billion. A sizeable part of the benefits in the early years of these 

programs has come from large reductions in the amount of direct and secondary PM emitted by 

the existing fleet of heavy-duty engines and vehicles, by requiring the use of the higher quality 

diesel fuel in these vehicles. While this proposed action may slightly increase some emissions, 

as explained in the previous section, we do not expect that these small increases will significantly 

diminish the health benefits of our stringent clean diesel standards. 

VIII. Public Participation 

We request comment by July 27, 2012 on all aspects of this proposal. This section 

describes how you can participate in this process. 

 

45 See Fuel Dosing Memo, note 39, above.
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A. How Do I Submit Comments? 

We are opening a formal comment period by publishing this document. We will accept 

comments through July 27, 2012. If you have an interest in the program described in this 

document, we encourage you to comment on any aspect of this rulemaking. We request comment 

on various topics throughout this proposal. 

Your comments will be most useful if you include appropriate and detailed supporting 

rationale, data, and analysis. If you disagree with parts of the proposed program, we encourage 

you to suggest and analyze alternate approaches to meeting the goals described in this proposal. 

You should send all comments, except those containing proprietary information, to our Air 

Docket (see ADDRESSES) before the end of the comment period. 

If you submit proprietary information for our consideration, you should clearly separate it 

from other comments by labeling it “Confidential Business Information (CBI).” You should send 

CBI directly to the contact person listed under FOR FURTHER INFORMATION CONTACT

instead of the public docket. This will help ensure that no one inadvertently places proprietary 

information in the docket. If you want us to use your confidential information as part of the basis 

for the final rule, you should send a non-confidential version of the document summarizing the 

key data or information. We will disclose information covered by a claim of confidentiality only 

through the application of procedures described in 40 CFR part 2. If you do not identify 

information as confidential when we receive it, we may make it available to the public without 

notifying you. 

EPA is also publishing a Direct Final Rule (DFR) addressing the emergency vehicle 

provisions described in Section IV of this document. If we receive adverse comments on the 

emergency vehicle provisions in this proposal by [Insert date 30 days from date of publication 

in the Federal Register], we will publish a timely withdrawal in the Federal Register informing 

the public that the direct final rule will not take effect, and we will complete the process of 

responding to comments and issuing a final rule. 

EPA is publishing the DFR to expedite the deployment of solutions that will best ensure 

the readiness of the nation’s emergency vehicles. We request that commenters identify in your 

comments any portions of the emergency vehicle proposed action described in Section IV above 

with which you agree and support as proposed, in addition to any comments regarding 

suggestions for improvement or provisions with which you disagree. In the case of a comment 

that is otherwise unclear whether it is adverse, EPA would interpret relevant comments calling 

for more flexibility or less restrictions for emergency vehicles as supportive of the direct final 

action. In this way, the EPA will be able to adopt those elements of the DFR that are fully 

supported and most needed today, while considering and addressing any adverse comments 

received on the proposed rule, in the course of developing the final rule. 

Note that Docket Number EPA-HQ-OAR-2011-1032 is being used for both the DFR and 

this Notice of Proposed Rulemaking (NPRM). 
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B. Will There Be a Public Hearing? 

We will hold a public hearing at the EPA’s National Vehicle and Fuels Emission 

Laboratory, 2565 Plymouth Road in Ann Arbor, Michigan on June 27, 2012. The hearing will 

start at 10:00 am and continue until everyone has had a chance to speak. 

If you would like to present testimony at the public hearing, we ask that you notify the 

contact person listed above under FOR FURTHER INFORMATION CONTACT at least ten 

days before the hearing. You should estimate the time you will need for your presentation and 

identify any needed audio/visual equipment. We suggest that you bring copies of your statement 

or other material for the EPA panel and the audience. It would also be helpful if you send us a 

copy of your statement or other materials before the hearing. 

We will make a tentative schedule for the order of testimony based on the notifications 

we receive. This schedule will be available on the morning of the hearing. In addition, we will 

reserve a block of time for anyone else in the audience who wants to give testimony. We will 

conduct the hearing informally, and technical rules of evidence won’t apply. We will arrange for 

a written transcript of the hearing and keep the official record of the hearing open for 30 days to 

allow you to submit supplementary information. You may make arrangements for copies of the 

transcript directly with the court reporter. 

IX. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review and Executive 

Order 13563: Improving Regulation and Regulatory Review

This action is not a “significant regulatory action” under the terms of Executive Order 

(EO) 12866 (58 FR 51735, October 4, 1993) and is therefore not subject to review under 

Executive Orders 12866 and 13563 (76 FR 3821, January 21, 2011). 

B. Paperwork Reduction Act

This action does not impose any new information collection burden. The proposed 

regulatory relief for emergency vehicles would be voluntary and optional, and the proposed 

revisions for engine and vehicle maintenance would merely codify existing guidelines. However, 

the Office of Management and Budget (OMB) has previously approved the information 

collection requirements contained in the existing regulations under the provisions of the 

Paperwork Reduction Act, 44 U.S.C. 3501 et seq. and has assigned OMB Control Numbers 

2060-0104 and 2060-0287. The OMB control numbers for EPA’s regulations in 40 CFR are 

listed in 40 CFR part 9. 

C. Regulatory Flexibility Act

The Regulatory Flexibility Act (RFA) generally requires an agency to prepare a 

regulatory flexibility analysis of any rule subject to notice and comment rulemaking 

requirements under the Administrative Procedure Act or any other statute unless the agency 
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certifies that the rule will not have a significant economic impact on a substantial number of 

small entities. Small entities include small businesses, small organizations, and small 

governmental jurisdictions. 

For purposes of assessing the impacts of this rule on small entities, small entity is defined 

as: (1) a small business primarily engaged in shipbuilding and repairing as defined by NAICS 

code 336611 with 1,000 or fewer employees (based on Small Business Administration size 

standards); (2) a small business that is primarily engaged in freight or passenger transportation 

on the Great Lakes as defined by NAICS codes 483113 and 483114 with 500 or fewer 

employees (based on Small Business Administration size standards); (3) a small business 

primarily engaged in commercial and industrial machinery and equipment repair and

maintenance as defined by NAICS code 811310 with annual receipts less than $7 million (based 

on Small Business Administration size standards); (4) a small governmental jurisdiction that is a 

government of a city, county, town, school district or special district with a population of less 

than 50,000; and (5) a small organization that is any not-for-profit enterprise which is 

independently owned and operated and is not dominant in its field. 

After considering the economic impacts of today’s proposed rule on small entities, I 

certify that proposed rule would not have a significant economic impact on a substantial number 

of small entities. 

In determining whether a rule has a significant economic impact on a substantial number 

of small entities, the impact of concern is any significant adverse economic impact on small 

entities, since the primary purpose of the regulatory flexibility analyses is to identify and address 

regulatory alternatives “which minimize any significant economic impact of the rule on small 

entities.” 5 U.S.C. 603 and 604. Thus, an agency may certify that a rule will not have a 

significant economic impact on a substantial number of small entities if the rule relieves 

regulatory burden, or otherwise has a positive economic effect on all of the small entities subject 

to the rule. 

This proposed rule provides regulatory relief related to emergency vehicles and codifies 

existing guidelines related to engine and vehicle maintenance. As such, we anticipate no costs 

and therefore no regulatory burden associated with this rule. We have concluded that this rule 

will not increase regulatory burden for affected small entities.

D. Unfunded Mandates Reform Act

This proposal contains no Federal mandates under the regulatory provisions of Title II of 

the UMRA for State, local, or tribal governments. The proposal imposes no enforceable duty on 

any State, local or tribal governments. EPA has determined that this proposal contains no 

regulatory requirements that might significantly or uniquely affect small governments. The 

agency has determined that this proposal does not contain a Federal mandate that may result in 

expenditures of $100 million or more for the private sector in any one year. Manufacturers have 

the flexibility and will likely choose whether or not to use optional AECD’s based on their 

strategies for complying with the applicable emissions standards. Similarly, manufacturers may 

choose to use DEF maintenance intervals longer than the minimums proposed in this action, and 
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Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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manufacturers may elect to use SCR strategies that consume lower amounts of DEF. Thus, 

today’s proposal is not subject to the requirements of sections 202 and 205 of the UMRA. 

E. Executive Order 13132: Federalism

Executive Order 13132, entitled “Federalism” (64 FR 43255, August 10, 1999), requires 

EPA to develop an accountable process to ensure “meaningful and timely input by State and 

local officials in the development of regulatory policies that have federalism implications.” 

“Policies that have federalism implications” is defined in the Executive Order to include 

regulations that have “substantial direct effects on the States, on the relationship between the 

national government and the States, or on the distribution of power and responsibilities among 

the various levels of government.” 

This proposed action does not have federalism implications. It will not have substantial 

direct effects on the States, on the relationship between the national government and the States, 

or on the distribution of power and responsibilities among the various levels of government, as 

specified in Executive Order 13132. This proposed rule would apply to manufacturers of heavyduty diesel engines and not to state or local governments. Thus, Executive Order 13132 does not 

apply to this action. 

In the spirit of Executive Order 13132, and consistent with EPA policy to promote 

communications between the agency and State and local governments, the agency specifically 

solicits comment on this proposed action from State and local officials. 

F. Executive Order 13175: Consultation and Coordination with Indian 

Tribal Governments

This action does not have tribal implications, as specified in Executive Order 13175 (65 

FR 67249, November 9, 2000). This proposal will be implemented at the Federal level and 

would impose compliance costs only on affected engine manufacturers depending on the extent 

to which they take advantage of the flexibilities offered. Tribal governments would be affected 

only to the extent they purchase and use vehicles with regulated engines. Thus, Executive Order 

13175 does not apply to this proposed rule. EPA specifically solicits additional comment on this 

proposed action from tribal officials. 

G. Executive Order 13045: Protection of Children from Environmental 

Health and Safety Risks

Executive Order 13045: “Protection of Children from Environmental Health Risks and 

Safety Risks” (62 FR 19885, April 23, 1997) applies to any rule that: (1) is determined to be 

“economically significant” as defined under Executive Order 12866, and (2) concerns an 

environmental health or safety risk that EPA has reason to believe may have a disproportionate 

effect on children. If the regulatory action meets both criteria, the agency must evaluate the 

environmental health or safety effects of the planned rule on children, and explain why the 

planned regulation is preferable to other potentially effective and reasonably feasible alternatives 

considered by the agency.
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EPA interprets Executive Order 13045 as applying only to those regulatory actions that 

are based on health or safety risks, such that the analysis required under section 5-501 of the 

Order has the potential to influence the regulation. This proposed rule is not subject to Executive 

Order 13045 because it does not establish an environmental standard intended to mitigate health 

or safety risks. 

H. Executive Order 13211: Energy Effects 

This proposed action is not subject to Executive Order 13211 (66 FR 28355 (May 22, 

2001)), because it is not a significant regulatory action under Executive Order 12866. 

I. National Technology Transfer Advancement Act

Section 12(d) of the National Technology Transfer and Advancement Act of 1995 

(“NTTAA”), Public Law No. 104-113, 12(d) (15 U.S.C. 272 note) directs EPA to use voluntary 

consensus standards in its regulatory activities unless to do so would be inconsistent with 

applicable law or otherwise impractical. Voluntary consensus standards are technical standards 

(e.g., materials, specifications, test methods, sampling procedures, and business practices) that 

are developed or adopted by voluntary consensus standards bodies. NTTAA directs EPA to 

provide Congress, through OMB, explanations when the Agency decides not to use available and 

applicable voluntary consensus standards. 

 This action does not involve technical standards. Therefore, EPA is not considering the use of 

any voluntary consensus standards. 

 

J. Executive Order 12898: Federal Actions to Address Environmental 

Justice in Minority Populations and Low-Income Populations

Executive Order 12898 (59 FR 7629 (Feb. 16, 1994)) establishes federal executive policy 

on environmental justice. Its main provision directs federal agencies, to the greatest extent 

practicable and permitted by law, to make environmental justice part of their mission by 

identifying and addressing, as appropriate, disproportionately high and adverse human health or 

environmental effects of their programs, policies, and activities on minority populations and lowincome populations in the United States. 

EPA has determined that this proposed rule would not have disproportionately high and 

adverse human health or environmental effects on minority or low-income populations. This 

action is expected to increase the level of environmental protection for all affected populations 

because this proposed rule increases the ways that manufacturers can demonstrate compliance 

with heavy-duty engine standards. 

List of Subjects

40 CFR Part 85 
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Confidential business information, Imports, Labeling, Motor vehicle pollution, Reporting and 

recordkeeping requirements, Research, Warranties.

40 CFR Part 86 

Administrative practice and procedure, Confidential business information, Motor vehicle 

pollution, Reporting and recordkeeping requirements. 

40 CFR Part 1039 

Administrative practice and procedure, Air pollution control, Confidential business information, 

Environmental protection, Imports, Labeling, Penalties, Reporting and recordkeeping 

requirements, Warranties.

Dated: __________________________________ 

_______________________________________ 

Lisa P. Jackson

Administrator

For the reasons set forth in the preamble, the Environmental Protection Agency proposes to 

amend title 40, chapter I of the Code of Federal Regulations as follows: 

PART 85— CONTROL OF AIR POLLUTION FROM MOBILE SOURCES

1. The authority citation for part 85 continues to read as follows: 

Authority: 42 U.S.C. 7401-7671q. 

Subpart R–[Amended]

2. Add §85.1716 to subpart R to read as follows: 

§ 85.1716 Approval of an emergency vehicle field modification (EVFM).

This section describes how you may implement design changes for an emergency vehicle that 

has already been placed into service to ensure that the vehicle will perform properly in 

emergency situations. This applies for any light-duty vehicle, light-duty truck, or heavy-duty 

vehicle meeting the definition of emergency vehicle in 40 CFR 86.004-2 or 86.1803. In this 

section, “you” refers to the certifying manufacturer and “we” refers to the EPA Administrator 

and any authorized representatives. 

(a) You must notify us in writing of your intent to install or distribute an emergency vehicle field 

modification (EVFM). In some cases you may install or distribute an EVFM only with our 

advance approval, as specified in this section. 

(b) Include in your notification a full description of the EVFM and any documentation to support 

your determination that the EVFM is necessary to prevent the vehicle from losing speed, torque, 

or power due to abnormal conditions of its emission control system, or to prevent such abnormal 

conditions from occurring during operation related to emergency response. Examples of such 

abnormal conditions may include excessive exhaust backpressure from an overloaded particulate 

trap, or running out of diesel exhaust fluid for engines that rely on urea-based selective catalytic 

reduction. Your determination must be based on an engineering evaluation or testing or both. 

(c) You may need our advance approval for your EVFM, as follows: 
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(1) Where the proposed EVFM is identical to an AECD we approved under this part for an 

engine family currently in production, no approval of the proposed EVFM is necessary.

(2) Where the proposed EVFM is for an engine family currently in production but the 

applicable demonstration is based on an AECD we approved under this part for an engine 

family no longer in production, you must describe to us how your proposed EVFM differs 

from the approved AECD. Unless we say otherwise, your proposed EVFM is deemed 

approved 30 days after you notify us.

(3) If we have not approved an EVFM comparable to the one you are proposing, you must 

get our approval before installing or distributing it. In this case, we may request additional 

information to support your determination under paragraph (b) of this section, as follows: 

(i) If we request additional information and you do not provide it within 30 days after we 

ask, we may deem that you have retracted your request for our approval; however, we 

may extend this deadline for submitting the additional information. 

(ii) We will deny your request if we determine that the EVFM is not necessary to prevent 

the vehicle from losing speed, torque, or power due abnormal conditions of the emission 

control system, or to prevent such abnormal conditions from occurring, during operation 

related to emergency response.

(iii) Unless we say otherwise, your proposed EVFM is deemed approved 30 days after we 

acknowledge that you have provided us with all the additional information we have 

specified.

(4) If your proposed EVFM is deemed to be approved under paragraph (c)(2) or (3) of this 

section and we find later that your EVFM in fact does not meet the requirements of this 

section, we may require you to no longer install or distribute it.

PART 86--CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY 

VEHICLES AND ENGINES

3. The authority citation for part 86 continues to read as follows: 

Authority: 42 U.S.C. 7401-7671q. 

Subpart A–[Amended]

4. Section 86.004-2 is amended as follows: 

a. By adding a definition for “Ambulance” in alphabetical order.

b. By revising the definition for “Defeat device”. 

c. By adding definitions for “Diesel exhaust fluid”, “Emergency vehicle”, and “Fire truck” in 

alphabetical order.

§ 86.004–2 Definitions.

* * * * * 

Ambulance has the meaning given in §86.1803. 

Defeat device means an auxiliary emission control device (AECD) that reduces the 

effectiveness of the emission control system under conditions which may reasonably be expected 

to be encountered in normal vehicle operation and use, unless: 

(1) Such conditions are substantially included in the applicable Federal emission test procedure 

for heavy-duty vehicles and heavy-duty engines described in subpart N of this part; 

(2) The need for the AECD is justified in terms of protecting the vehicle against damage or 

accident; 

(3) The AECD does not go beyond the requirements of engine starting; or
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(4) The AECD applies only for engines that will be installed in emergency vehicles, and the need 

is justified in terms of preventing the engine from losing speed, torque, or power due abnormal 

conditions of the emission control system, or in terms of preventing such abnormal conditions 

from occurring, during operation related to emergency response. Examples of such abnormal 

conditions may include excessive exhaust backpressure from an overloaded particulate trap, and 

running out of diesel exhaust fluid for engines that rely on urea-based selective catalytic 

reduction. 

Diesel exhaust fluid (DEF) has the meaning given in §86.1803. 

Emergency vehicle means a vehicle that is an ambulance or a fire truck. 

Fire truck has the meaning given in §86.1803. 

* * * * * 

5. Section 86.004-25 is amended as follows: 

a. By revising paragraph the introductory text of (b)(4).

b. By adding paragraph (b)(4)(v). 

c. By revising paragraph the introductory text of (b)(6)(i) and (b)(6)(i)(H).

d. By adding paragraph (b)(6)(i)(I). 

§ 86.004-25 Maintenance.

* * * * * 

(b) * * * 

(4) For diesel-cycle heavy-duty engines, emission-related maintenance in addition to or at 

shorter intervals than the following specified values will not be accepted as technologically 

necessary, except as provided in paragraph (b)(7) of this section: 

* * * * * 

(v) For engines that use selective catalytic reduction, the replenishment of diesel exhaust fluid 

shall occur according to the following schedule: 

(A) For heavy-duty engines in vocational vehicles such as dump trucks, concrete mixers, 

refuse trucks and similar applications that are typically centrally fueled, at an interval, in 

miles or hours of vehicle operation, that is no less than the vehicle’s fuel capacity. 

(B) For all other heavy-duty engines, at an interval, in miles or hours of vehicle operation, 

that is no less than twice the vehicle’s fuel capacity.

* * * * * 

(6)(i) The following components are defined as critical emission-related components:

* * * * * 

(H) Components comprising the selective catalytic reduction system (including diesel exhaust 

fluid tank). 

(I) Any other component whose primary purpose is to reduce emissions or whose failure would 

commonly increase emissions of any regulated pollutant without significantly degrading engine 

performance. 

* * * * * 

6. Section 86.0004-28 is amended by revising the introductory text of paragraph (i) to read as 

follows: 

§ 86.004-28 Compliance with emission standards.

* * * * * 
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(i) Emission results from heavy-duty engines equipped with exhaust aftertreatment may need to 

be adjusted to account for regeneration events. This provision only applies for engines equipped 

with emission controls that are regenerated on an infrequent basis. For the purpose of this 

paragraph (i), the term “regeneration” means an event during which emission levels change 

while the aftertreatment performance is being restored by design. Examples of regenerations are 

increasing exhaust gas temperature to remove sulfur from an adsorber or increasing exhaust gas 

temperature to oxidize PM in a trap. For the purpose of this paragraph (i), the term “infrequent” 

means having an expected frequency of less than once per transient test cycle. Calculation and 

use of adjustment factors are described in paragraphs (i)(1)–(5) of this section. If your engine 

family includes engines with one or more AECDs for emergency vehicle applications approved 

under paragraph (4) of the definition of defeat device, do not consider additional regenerations 

resulting from those AECDs when calculating emission factors or frequencies under this 

paragraph (i).

* * * * * 

7. Section 86.095-35 is amended by revising paragraph (a)(3)(iii)(O) to read as follows: 

§ 86.095-35 Labeling. 

(a) * * * 

(3) * * * 

(iii) * * * 

(O) For engines with one or more approved AECDs for emergency vehicle applications under 

paragraph (4) of the definition of defeat device, the statement: “THIS ENGINE IS FOR 

INSTALLATION IN EMERGENCY VEHICLES ONLY.”

* * * * * 

Subpart B–[Amended]

8. Section 86.131-00 is amended by adding paragraph (g) to read as follows: 

§ 86.131-00 Vehicle preparation.

* * * * * 

(g) You may disable any AECDs that have been approved solely for emergency vehicle 

applications under paragraph (4) of the definition of defeat device. The emission standards do 

not apply when any of these AECDs are active.

Subpart N–[Amended]

9. Section 86.1305-2010 is amended by adding paragraph (i) to read as follows: 

§ 86.1305-2010 Introduction; structure of subpart.

* * * * * 

(i) You may disable any AECDs that have been approved solely for emergency vehicle 

applications under paragraph (4) of the definition of defeat device. The emission standards do 

not apply when any of these AECDs are active.

10. Section 86.1370-2007 is amended by adding paragraph (h) to read as follows: 

§ 86.1370-2007 Not-To-Exceed test procedures. 

* * * * * 
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(h) Emergency vehicle AECDs. If your engine family includes engines with one or more 

approved AECDs for emergency vehicle applications under paragraph (4) of the definition of 

defeat device, the NTE emission limits do not apply when any of these AECDs are active. 

Subpart S–[Amended]

11. Section 86.1803-01 is amended as follows: 

a. By adding a definition for “Ambulance” in alphabetical order.

b. By revising the definition for “Defeat device”. 

c. By adding definitions for “Diesel exhaust fluid”, “Emergency vehicle”, and “Fire truck” in 

alphabetical order.

§ 86.1803-01 Definitions.

* * * * * 

 Ambulance means a vehicle used for emergency medical care that provides all of the 

following: 

(1) A driver’s compartment.

(2) A patient compartment to accommodate an emergency medical services provider and one 

patient located on the primary cot so positioned that the primary patient can be given intensive 

life-support during transit. 

(3) Equipment and supplies for emergency care at the scene as well as during transport. 

(4) Safety, comfort, and avoidance of aggravation of the patient’s injury or illness. 

(5) Two-way radio communication. 

(6) Audible and visual traffic warning devices. 

* * * * * 

Defeat device means an auxiliary emission control device (AECD) that reduces the 

effectiveness of the emission control system under conditions which may reasonably be expected 

to be encountered in normal vehicle operation and use, unless: 

(1) Such conditions are substantially included in the Federal emission test procedure; 

(2) The need for the AECD is justified in terms of protecting the vehicle against damage or 

accident;

(3) The AECD does not go beyond the requirements of engine starting; or 

(4) The AECD applies only for emergency vehicles and the need is justified in terms of 

preventing the vehicle from losing speed, torque, or power due to abnormal conditions of the 

emission control system, or in terms of preventing such abnormal conditions from occurring, 

during operation related to emergency response. Examples of such abnormal conditions may 

include excessive exhaust backpressure from an overloaded particulate trap, and running out of 

diesel exhaust fluid for engines that rely on urea-based selective catalytic reduction.

* * * * * 

Diesel exhaust fluid (DEF) means a liquid compound used in conjunction with selective 

catalytic reduction to reduce NOX emissions. Diesel exhaust fluid is generally understood to 

conform to the specifications of ISO 22241. 

* * * * * 

Emergency vehicle means a vehicle that is an ambulance or a fire truck.

* * * * * 
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Fire truck means a vehicle designed to be used under emergency conditions to transport 

personnel and equipment and to support the suppression of fires and mitigation of other 

hazardous situations. 

* * * * * 

12. Section 86.1807-01 is amended by adding paragraphs (h) and (i) to read as follows: 

§ 86.1807-01 Vehicle labeling.

* * * * * 

(h) Vehicles powered by model year 2007 through 2013 diesel-fueled engines must include 

permanent readily visible labels on the dashboard (or instrument panel) and near all fuel inlets 

that state “Use Ultra Low Sulfur Diesel Fuel Only” or “Ultra Low Sulfur Diesel Fuel Only”.

(i) For vehicles with one or more approved AECDs for emergency vehicles under paragraph (4) 

of the definition of defeat device, include the following statement on the emission control 

information label: “THIS VEHICLE HAS A LIMITED EXEMPTION AS AN EMERGENCY 

VEHICLE.”

13. Subpart S is amended by removing §86.1807-07. 

§86.1807-07 – [Removed] 

14. Section 86.1834-01 is amended as follows: 

a. By revising paragraph the introductory text of (b)(4).

b. By adding paragraph (b)(4)(iii). 

c. By revising paragraph (b)(6)(i)(H).

d. By adding paragraph (b)(6)(i)(I). 

§ 86.1834-01 Allowable maintenance. 

* * * * * 

(b) * * * 

(4) For diesel-cycle vehicles, emission-related maintenance in addition to, or at shorter intervals 

than the following will not be accepted as technologically necessary, except as provided in 

paragraph (b)(7) of this section: 

* * * * * 

(iii) For vehicles that use selective catalytic reduction, the replenishment of diesel exhaust fluid 

shall occur at an interval, in miles or hours of vehicle operation, that is no less than the scheduled 

oil change interval. 

* * * * * 

(6) * * * 

(i) * * * 

(H) Components comprising the selective catalytic reduction system (including diesel exhaust 

fluid tank). 

(I) Any other component whose primary purpose is to reduce emissions or whose failure would 

commonly increase emissions of any regulated pollutant without significantly degrading engine 

performance.

* * * * * 

15. Section 86.1840-01 is amended by revising paragraph (c) to read as follows: 

§ 86.1840-01 Special test procedures.
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* * * * * 

(c) Manufacturers of vehicles equipped with periodically regenerating aftertreatment devices 

must propose a procedure for testing and certifying such vehicles, including SFTP testing, for the 

review and approval of the Administrator. The manufacturer must submit its proposal before it 

begins any service accumulation or emission testing. The manufacturer must provide with its 

submittal sufficient documentation and data for the Administrator to fully evaluate the operation 

of the aftertreatment devices and the proposed certification and testing procedure. 

* * * * * 

PART 1039–CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD 

COMPRESSION-IGNITION ENGINES

16. The authority citation for part 1039 continues to read as follows: 

Authority: 42 U.S.C. 7401-7671q. 

Subpart B–[Amended]

17. Section 1039.115 is amended by adding paragraphs (g)(4) and (g)(5) to read as follows: 

§1039.115 What other requirements apply?

* * * * * 

(g) * * * 

(4) The auxiliary emission control device applies only for engines that will be installed in 

emergency equipment and the need is justified in terms of preventing the equipment from 

losing speed or power due to abnormal conditions of the emission control system, or in terms 

of preventing such abnormal conditions from occurring, during operation related to 

emergency response. Examples of such abnormal conditions may include excessive exhaust 

backpressure from an overloaded particulate trap, and running out of diesel exhaust fluid for 

engines that rely on urea-based selective catalytic reduction. The emission standards do not 

apply when any AECDs approved under this paragraph (g)(4) are active. 

(5) The auxiliary emission control device operates only in emergency situations as defined in 

§1039.665 and meets all of the requirements of that section, and you meet all of the 

requirements of that section.

18. Section 1039.125 is amended by adding paragraphs (a)(2)(iii) and (a)(3)(iii) to read as 

follows: 

§ 1039.125 What maintenance instructions must I give to buyers? 

* * * * * 

(a) * * * 

(2) * * * 

(iii) For SCR systems, the minimum interval for replenishing the diesel exhaust fluid is the 

number of engine operating hours necessary to consume a full tank of fuel based on normal 

usage starting from full fuel capacity for the equipment. 

(3) * * * 

(iii) For SCR systems, the minimum interval for replenishing the diesel exhaust fluid is the 

number of engine operating hours necessary to consume a full tank of fuel based on normal 

usage starting from full fuel capacity for the equipment. 

* * * * * 
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19. Section 1039.130 is amended by revising paragraph (b)(3) to read as follows: 

§ 1039.130 What installation instructions must I give to equipment manufacturers?

* * * * * 

(b) * * * 

(3) Describe the instructions needed to properly install the exhaust system and any other 

components. Include instructions consistent with the requirements of §1039.205(u). Also 

describe how to properly size diesel exhaust fluid reservoirs consistent with the specifications in 

§1039.125(a) if applicable. 

* * * * * 

20. Section 1039.135 is amended by adding paragraph (c)(15) to read as follows: 

§1039.135 How must I label and identify the engines I produce? 

* * * * * 

(c) * * * 

(15) For engines with one or more approved auxiliary emission control devices for emergency 

equipment applications under §1039.115(g)(4), the statement: “THIS ENGINE IS FOR 

INSTALLATION IN EMERGENCY EQUIPMENT ONLY.”

 * * * * * 

Subpart F–[Amended]

21. Section 1039.501 is amended by adding paragraph (g) to read as follows: 

§ 1039.501 How do I run a valid emission test? 

* * * * * 

(g) You may disable any AECDs that have been approved solely for emergency equipment 

applications under §1039.115(g)(4). 

22. Section 1039.525 is amended by revising the introductory text to read as follows: 

§ 1039.525 How do I adjust emission levels to account for infrequently regenerating 

aftertreatment devices?

This section describes how to adjust emission results from engines using aftertreatment 

technology with infrequent regeneration events. For this section, “regeneration” means an 

intended event during which emission levels change while the system restores aftertreatment 

performance. For example, exhaust gas temperatures may increase temporarily to remove sulfur 

from adsorbers or to oxidize accumulated particulate matter in a trap. For this section, 

“infrequent” refers to regeneration events that are expected to occur on average less than once 

over the applicable transient duty cycle or ramped-modal cycle, or on average less than once per 

typical mode in a discrete-mode test. If your engine family includes engines with one or more 

AECDs for emergency equipment applications approved under §1039.115(g)(4), do not consider 

additional regenerations resulting from those AECDs when calculating emission factors or 

frequencies under this section. 

* * * * * 
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Subpart G–[Amended]

23. A new §1039.665 is added to subpart G to read as follows: 

§1039.665 Special provisions for use of engines in emergency situations. 

This section specifies provisions that allow for AECDs that are necessary to ensure proper 

functioning of engines and equipment regulated under this part in emergency situations. For 

purposes of this section, an emergency situation is one in which the functioning (or 

malfunctioning) of emission controls poses a significant risk to human life. For example, a 

situation in which a feature of emission controls inhibits the performance of an engine being 

used to rescue a person from a life-threatening situation would be an emergency situation. 

AECDs approved under this section are not defeat devices. 

(a) Manufacturers may ask for approval under this section at any time; however, we encourage 

manufacturers to obtain preliminary approval before submitting an application for certification. 

We may allow manufacturers to apply an approved emergency AECD to engines and equipment 

that have already been placed into service.

(b) We will approve an AECD where we determine the following criteria are met:

(1) Activation of the AECD cannot occur without the specific permission of the certificate 

holder, and must require the input of a temporary code or equivalent security feature. 

(2) The AECD must become inactive within 24 engine hours of becoming active. 

(3) The AECD may deactivate emission controls as necessary to address the emergency 

situation. For purposes of this paragraph (b)(3), inducement strategies related to operating 

SCR-equipped engines without reductant are considered to be emission controls. 

(4) The AECD’s design is consistent with good engineering judgment. 

(c) The certificate holder must keep records to document requests for and use of emergency 

AECDs under this section. 

(1) The operator (or other person responsible for the engine/equipment) must send a written 

request to the certificate holder prior to use, or a written confirmation of a verbal request 

within 30 days of making the request, including a description of the emergency situation, the 

reason for the use of the AECD, and a signature from an official acknowledging the 

conditions of the emergency situation (such as a county sheriff, fire marshal, or hospital 

administrator). Such requests are deemed to be submissions to EPA. Where written 

confirmation is not submitted by the operator, we will deem operation of the engine with an 

activated emergency AECD to be a violation of 40 CFR 1068.101(b)(1). 

(2) If the operator does not submit the applicable confirmation within 30 days, the certificate 

holder must send written notification to the operator that failure to submit written 

confirmation may subject the operator to penalties under 40 CFR 1068.101. 

(3) Within 60 days of the end of each calendar year in which the certificate holder authorizes 

use of the AECD, the certificate holder must send a report to the Designated Compliance 

Officer to summarize such use, including a description of the emergency situation 

precipitating each use, and copies of the written confirmation provided by operators (or 

statements that the operator did not provide confirmation). We may require more frequent 

reporting if we find that the certificate holder does not collect or attempt to collect written 

confirmation for each situation. 

(d) We may set other reasonable conditions to ensure that this provision is not used to 

circumvent the emission standards of this part. 

24. A new §1039.670 is added to subpart G to read as follows: 
This document is a prepublication version, signed by the Administrator of the Environmental Protection Agency, 

Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

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§ 1039.670 Approval of an emergency equipment field modification (EEFM).

This section describes how you may implement design changes for emergency equipment that 

has already been placed into service to ensure that the equipment will perform properly in 

emergency situations.

(a) You must notify us in writing of your intent to install or distribute an emergency equipment 

field modification (EEFM). In some cases you may install or distribute an EEFM only with our 

advance approval, as specified in this section. 

(b) Include in your notification a full description of the EEFM and any documentation to support 

your determination that the EEFM is necessary to prevent the equipment from losing speed, 

torque, or power due to abnormal conditions of its emission control system, or to prevent such 

abnormal conditions from occurring during operation related to emergency response. Examples 

of such abnormal conditions may include excessive exhaust backpressure from an overloaded 

particulate trap, or running out of diesel exhaust fluid (DEF) for engines that rely on urea-based 

selective catalytic reduction. Your determination must be based on an engineering evaluation or 

testing or both. 

(c) You may need our advance approval for your EEFM, as follows: 

(1) Where the proposed EEFM is identical to an AECD we approved under this part for an 

engine family currently in production, no approval of the proposed EEFM is necessary. 

(2) Where the proposed EEFM is for an engine family currently in production but the 

applicable demonstration is based on an AECD we approved under this part for an engine 

family no longer in production, you must describe to us how your proposed EEFM differs 

from the approved AECD. Unless we say otherwise, your proposed EEFM is deemed 

approved 30 days after you notify us. 

(3) If we have not approved an EEFM comparable to the one you are proposing, you must get 

our approval before installing or distributing it. In this case, we may request additional 

information to support your determination under paragraph (b) of this section, as follows: 

(i) If we request additional information and you do not provide it within 30 days after we 

ask, we may deem that you have retracted your request for our approval; however, we 

may extend this deadline for submitting the additional information.

(ii) We will deny your request if we determine that the EEFM is not necessary to prevent 

the equipment from losing speed, torque, or power due abnormal conditions of the 

emission control system, or to prevent such abnormal conditions from occurring, during 

operation related to emergency response.

(iii) Unless we say otherwise, your proposed EEFM is deemed approved 30 days after we 

acknowledge that you have provided us with all the additional information we have 

specified.

(4) If your proposed EEFM is deemed to be approved under paragraph (c)(2) or (3) of this 

section and we find later that your EEFM in fact does not meet the requirements of this 

section, we may require you to no longer install or distribute it.

Subpart I–[Amended]

25. Section 1039.801 is amended by adding definitions for “Diesel exhaust fluid” and 

“Emergency equipment” in alphabetical order to read as follows: 

§ 1039.801 What definitions apply to this part? 

* * * * * 
This document is a prepublication version, signed by the Administrator of the Environmental Protection Agency, 

Lisa Jackson, on May 23, 2012. We have taken steps to ensure the accuracy of this version, but it is not the official 

version.

Page 68 of 68

Diesel exhaust fluid (DEF) means a liquid compound used in conjunction with selective 

catalytic reduction to reduce NOX emissions. Diesel exhaust fluid is generally understood to 

conform to the specifications of ISO 22241. 

* * * * * 

 Emergency equipment means either of the following types of equipment: 

(1) Specialized vehicles used to perform aircraft rescue and fire-fighting functions at airports, 

with particular emphasis on saving lives and reducing injuries coincident with aircraft fires 

following impact or aircraft ground fires. 

(2) Wildland fire apparatus, which includes any apparatus equipped with a slip-on fire-fighting 

module, designed primarily to support wildland fire suppression operations. 

* * * * * 

26. Section 1039.805 is amended by adding abbreviations for “DEF”, “EEFM”, “ISO”, and 

“SCR” in alphabetical order to read as follows: 

§ 1039.805 What symbols, acronyms, and abbreviations does this part use? 

* * * * * 

DEF Diesel exhaust fluid.

EEFM Emergency equipment field modification. 

* * * * * 

ISO International Organization for Standardization (see www.iso.org). 

* * * * * 

SCR Selective catalytic reduction. 

* * * * *