UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D.C. 20460 

### MAR 

## 27 2007

CISD -07- 

### 07(LDV/LDT/MDPV/HDV/HDE) OFFICE OF AIR AND RADIATION
Dear Manufacturer:
SUBJECT: Certification Procedure for Light-Duty and Heavy-Duty Diesel Vehicles and Heavy-Duty Diesel Engines Using Selective Catalyst Reduction (SCR) Technologies
I. Background
On February 10,2000, EPA published the Tier 2 emission standards for light-duty vehicles and trucks. These standards established common, “fuel neutral” emission requirements for gasoline and diesel vehicles. They also set common standards for all passenger cars, light trucks, and medium-duty passenger vehicles. The Tier 2 standards allow emission averaging and require new vehicles to meet an average NOx emission level of 

### 0.07 grams per mile 

### (glmi). On January 

### 18,2001, EPA published 

### a rule setting stringent new requirements for heavy-duty highway engines and vehicles starting in 

### 2007. Manufacturers plan to meet these requirements by optimizing engine designs for low emissions and adding high-efficienc 

### y aftertreatment. The diesel engine NOx standard, which is phased-in between model years 2007 and 2010, is 0.20 grams per brake horsepower-hour (g/bhp-hr). Diesel engine and vehicle manufacturers have examined the use of several different types of 

### NOx reduction technologies in order to meet these requirements. One type of 

### NOx reducing technology, selective catalyst reduction (SCR), is of particular interest to diesel manufacturers because it can achieve as high as 

### 90% 

### NOx conversion efficiencies. An SCR system uses a nitrogen containing reducing agent (usually ammonia or urea) injected into the exhaust gas upstream of the catalyst. The reducing agent needs to be periodically replenished. Without the reducing agent, the efficiency of the SCR catalyst drops to zero and NOx emissions can increase substantially. The purpose of this letter is to discuss our intended approach for the certification of lightduty and heavy-duty diesel vehicles and heavy-duty diesel engines using SCR systems. The information in this letter reflects our current thinking. We recognize that SCR technology is still evolving and reserve the right to make any necessary changes to our approach for certification of light-duty and heavy-duty diesel vehicles and heavy-duty diesel engines using SCR systems that we deem appropriate. We also recognize that efforts currently underway by manufacturers, including infrastructure development, could help address some of the issues raised in this guidance prior to EPA’s review of individual certifications.

Internet Address (URL) http://www.epa.gov RecycledlRecyclable Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled PaperII. Regulatory Requirem e nts There are several regulatory requirem e nts that can imp act the certif icatio n and imple m entation of SCR for light-duty and h eavy-duty diesel vehicles and heavy-duty diesel engines. Two requirem e nt s of particular importance are: 40 CFR §86.004-25, §86.094-25 & §86.1834-01 A llowable Maintenance; and 40 CFR §86.094-22 & §86.1833-01 Adjustable Param e ters A. Allowable Maintenance Maintenance perform e d on vehicles, engine s, subsystem s , or components used to determine exhaust, evaporative, or refueling emission deterioration fact ors is classified as either emission-related or non-emission-related, and as either scheduled or un-scheduled. EPA considers service operations perfor m e d on SCR syste m s and which m eet the definition s o f “e mi ssion-related m a intenance” at §86.088-02 and §86.1803-01 and “scheduled m a intenance” at §86.082 -2 and §86.1 803-01 to be emission-related schedu led m a intenance. Emission-related scheduled m a intenance is consid ered technologically necessary to ensure in -us e comp liance with the emission stan dards. Man u facturers must determine the technological need for m a intenance using good engineering judgm ent. 40 CFR §86.094-25(b)(3) and (4) and §86.1834-01( b)(3) and (4) establish mi nimu m allowable maintenance intervals for vari ous emission-related technologies. EPA determined that emission -related m a intenance at interva l s sho rter than tho s e lis ted in paragraphs (b)(3) and (4) are not technologi cally necessary. However, there is a provision in paragraph (b)(7) th at allo ws a m a nuf acture r to req u est a ch ang e to the scheduled m a intenance interval, including an in terval sho rter than pres cribed in (b)(3) and (4). For diesel-cycle light-duty vehicles and light -duty trucks, emission -re late d m a intenan ce, such as the adjustm e nt, cleaning, repair or re placem ent of the catalytic converter can not occur before 100,000 miles of use or before 100,000 mile intervals thereafter. For dieselcycle heavy-duty engines, emission-relate d m a intenance can not occur before 100,000 miles of use or before 100,000 mile intervals thereafter for light heavy-duty engines, or before 150,000 mile intervals thereafter for m e dium and heavy heavy-duty engines. Since the S CR catalyst does not function withou t the use of a reducing agent, we believe 40 CFR §86.1834-01(b)(4)(ii)(F ) and §86.004-25(b )(4)(iii)(F) would apply to the SC R catalyst and all of the ass o ciated hard ware , including but not li mited to, the reducing agent, th e reducing agen t storage tan k, the dos in g valve, and all lines and hoses. Because of packaging constraints, m a ny m a nufacturers have indicated th at they would not be able to equip their vehicles with reducing agent st orage tanks of sufficient size to allow for mi ni mu m reducing agent refill intervals that m eet the re quired interv als of 100,000 or 150,000 miles. In order for EPA to consider a change to the scheduled m a intenance interval per paragraph (b )(7), the Admi nistrator must approve a request for approval indicating that the requested change in m a intenance schedule is “new,” m e a n ing the m a intenance did not exist prior to the 1980 model year, and th at the new m a intenance interval is technologically necessary. If EPA approves a request for new sche duled m a intenance, 2the Agency must announce in the Federal Regi ster the designation of emission-related m a intenance item s , along with their identification as critical or non-critical, and the estab lishm ent of the technologically nece ssary m a intenance intervals. Unless m a nufacturers can develop an SCR s y stem th at only requires the replenishm ent of the reducing agent every 100,000 miles for light-duty and 150,000 miles for heavy-duty, it appears that m a nufacturers wanting to use SCR tec hnology will have to request a ch ange to scheduled m a intenance per 40 CFR §86.1834- 01(b)(7) or §86.094-25(b)(7). It m a y be appropriate for EPA to approve an industry- wide scheduled m a intenance change, as we have done previously in similar situations.
B. Adjustable Param e ter s 40 CFR §86.094-22 and §86.1833-01 authorize E P A to determine those vehicle or engine param e ters that will be subject to adjustm e ntfor emissions testing purposes. Paragraphs §86.094-22(e)(1) and §86.1833-01(a)(1) discuss how the Agency determi n es which param e ters are subject to adjustm e nt. Speci fically, the paragraphs state “The following param e ters m a y be subject to adjustm e nt: th e idle fuel-air mi xture parameter on Ottocycle veh i cles; th e chok e valve actio n param e te r(s) on carbureted, Otto -cycle vehicles (or engines); or any param e ter on any vehicle (O tto -c ycle or d i ese l ) which is p hysica lly capable of being adjusted, m a y significantly affect emissions, and was not present on the m a nufacturer’s veh i cles (or e ngines) in the previous m odel year in the sam e for m and function.” The Admi nistrator can also determine other param e ters to be subject to adjustm e nt under §86.094-22(e)(1)(ii) and §86.1 833-01(a)(1)(ii) but mu st provide notice and lead time
It is important to test a vehicle for emi ssions over the full range of an adjustable param e ter b ecause EPA needs to ens u re that the emission perfor m ance in-use is as go od as at certification. Since som e e miss i on co mponents and/or system s can be adjusted, there is a co ncern th at th e vehicle co uld be operated at settings other than the m a nufacturer’s recomm e nded setting possibly resulting in emissions levels that could exceed th e emission stan dards. Paragr aphs §86. 094-22(e)(2) and §86.1833-01(a)(2) state that a p aram e ter m a y be determined to be adequately inaccess i ble or sealed

. If a param e ter is determined to be adequately in acce ss ible o rsea l e d, the vehicle will on ly b e emission tes t ed at the ac tual se tting s to which the param e ter is adjusted du ring production. Paragraphs §86.094-22(e)(2)(iv) and §86.1833-01(a)(2)(iv) state that in determining the adequacy of a physical limit, stop, seal, or other m eans used to inhibit adjustm e nt of a param e ter not covered by paragr aph (a)(2)(i) or (ii) of this section, the following shall be considered: the likelihood th at it will be circum vented, rem oved, or exceeded onin-use veh i cles. Because the NOx efficiency and thus the NOx emissions perfor m a nce of an SCR system is so dependent on a nitrogen-c ontaining reducing agent, it is critical that a vehicle using SCR never operate without the reducing agent. Most SCR system designs rely on storing reducing agent in a tank lo cated on the vehicle and on the vehicle operator taking responsibility for refill ing the tank w ith reducing agent. This m eans that the vehicle operato r has to be m a de aware that reduci ng agent needs to replaced and that reducin g agent is available. W ithout a m echanism to inform the vehicle operator that the reducing agent need s to be rep l aced, and witho u t a readily available so urce of replacem ent 3reducing ag ent, there is a high likelihood that th e adjus t able param e ter will b e circumvented or exceed ed on in-use vehicles. T h erefore, we do not believe that an SCR system that requires the v e hicle operator to replace the reducing agent can be considered to be adequately inaccess ible o rsealed. As a result, it appears to EPA that an SCR system utilizing a reducing agent that needs to be periodically replenished would meet the definition set forth in paragraphs §86.094­ 22(e)(1) and §86.1833-01(a)(1) and could be cons idered an adjustable param e ter by the Agency. This m eans that we have the authority to test an SCR- equipped vehicle with varying levels of reducing ag ent in th e storag e tan k, or, theor e tically, witho u t any reducing agent at all. If th e vehicle is capable of m eeti ng the NOx standard without any reducing agent, we would not consider the SCR sy stem to be in violation of the standard. However, if the vehicle exceeds emissions st andards without reducing agent in th e tan k, we expect th at we would deny the certification b ecause the d e sign will be considered unacceptable. If the m a nufacturer c a n prove to EPA that the i r SCR syste mdesign will not run out of reducing agent in -use and thus not exceed th e emission standards, we m a y determine th at the d e signis acceptab l e and approve certification of the vehicle design.
The rem a inder of this gu idance docu m ent discusses the a c ce ptance c r iteria EPA will apply to assure that diesel vehicles or engines using SCR technology achieve the Agency goal of always m eeting emission standards in-use.
III. Adjus t ab le Param e ter Acceptan ce Criteria We have based our SCR adjustable param e te r acceptance criteria on the Agency’s goals of ensuring that SCR-equipped vehicles contro l emissions in use a nd, m o re specifically, that the redu cing agen t is readily available for andused in th es e vehicles w h erever and whenever they need it. We have divided th e acceptance crite r ia into two catego r ies :

• Vehicle co mpliance – o Ensure that vehicles are designed to m eet the emission s t and ards in -use and that drivers will not operate th e vehicle withem pty reducing agent tanks.
• Reducing agent availa bility and a ccessib i lity – o Ensure thatdriver s will find SCR-quality reducing agent when they need it. In addition, while not a specific acceptance criterion, we believe it will be important for m a nufacturers to educate poten tial users, service industry representatives, and other stakeholders about SCR system s and their sp ecial needs. These efforts would be in addition to the required vehicle labeling and owner’s m a nual inform ation that is already provided.

4A. Vehicle Comp liance The vehicle comp liance criteria are d i vided in to five different cat ego r ies. Manufacturers must satisf y all f i ve c a te gories. The catego r ies ar e as f o llows:
1. Driver warning system 2. Driver inducem e nt 3. Identification of incorrect reducing agent 4. Tamp er resistant d e sign 5. Durable design 1) Driver Warning System

. The emissions perform a nce of SCR-equipped vehicles is expressly reliant on having reducing agent in th e system

. Unl i ke all other m a jor e mission control devices, SCR system s require regular us e r interac tion to ensure the system is operating properly. It is thus critical that the oper a tor bo thknow when reducing agent is needed and have enoughtim e to replace it befo re it runs ou t. A properly d e signed driv er warning system should help address these c oncerns. Manufacturers would need to use a warning system consisting of visual and po ssibly audible alarm s infor ming the vehicle operator that reducing agent level is low and mu st soon be replenished. The warning system woul d need to es calate in intensity as the reducing agent level approaches empty, culminating in driver notifi cation that cannot be defeatedor ignored, and cannot be turned off without replenishm ent of the reduc ing agent. To provide appropriate notice, the visual portion of the warning system would, at a mi ni mu m, need to consist of a unique light or m e ssage indicat ing low reducing agent level. The light or m e ssage should be located on the dashboard or in a vehi cle m e ssage center. T h e warning light or m e ssage would need to be di fferent from the “check engine ” or “service engine soon” lights used for OBD or other m a intenance. The sym bol or m e ssage used as the warning indicator would need to unmi stakably communicate to the vehicle op erator that the reducing agent level is low. The warning light or m e ssage does not initially have to be continuously activated, but we would antic ipate that as the reducing agent level approache s empty the illumination o f the li ght or m e ssage would escalate, culminating with the light being continuously illumi nate d or the m e ssage continuously broadcast in the m e ssage center. All unique SCR system warning lights or m e ssages would need to be approved by EPA. The location of the warni ng light or m e ssage also would need to be approved by EPA.
Manufacturers should also consid er an audible component of the warning system

. W e would expect that as the re ducing ag ent lev e l app r oaches empty the aud i ble warning system woul d escalate. We also anticipate that m a nufacturers would design the warning system to activate w e ll in advance of the reducing agent running out. Depending on the range between reducing agent r e f ills ( a f unction of reducing agent s t orag e tank s i ze, r e ducing age n t dosing r a te, fuel consumption, and N O x generation), the warning system for light-duty vehicles should begin to activate, at approxim atel y 1,000 miles prior to th e reducing agent tank becomi ng empty. For heavy duty diesel vehicles we understand that factors in addition to those m e ntioned above affect the tim e betw een reducing agent refi lls. Vehicle weight class and the curren tloadbeing carried also a f f

ect the redu cin g agent r e f ill inte rvals, b u t 5even given this variability, we believe that the warning system should begin soon enough f

o r the operator to h a ve a d equate opp ortunity (e.g ., two ref u elings) to a l so ref ill the reducing agent. The Agency m a y approve initi ation of the warning system at shorter or longer periods if the m a nufacturer can dem ons trate that shorter or longer periods are reasonab l e. 2) Driver In ducement. The warning system s discussed abov e are a critical part of the vehicle compliance acceptance criteria. As noted a well designed warning system should prevent people from ope rating SCR-equipped ve hicles without reducing agent. However, we believe anadditional, even strong er dete rr ent will be. The r ef ore, som e last-reso rt, persuasive m easures to induce use r s to rep l enishthe redu cin g agent will be essentia l
A num b er of m e thods could be employed by m a nufacturers to induce users to replenish the redu cing agent bef o r e the tank be com e s empty. The design or m echanism used will ultim ately b e up to each m a nufacture r . Wh ile EPA will not p r escribe a sp ecific driver inducem ent design neces s ary to m eet our accep tance criteria, we be lieve the examples below could satisfy our objective for driv er inducem ent designs. Our objective is straightforward. The driver inducement de sign must be robust and onerous enough to ensure that users will not operate the vehicle with out reduc ing agent in the vehicle if th ey ignore or deactivate the warn ing system

. The driver inducement m echanism should not create undue safety concerns. The following are som e examples of driver inducem ent m e thodologies that we understand m a nufacturers are an alyzing as part of their overall system designs. W e believ e othe r options thatcan m eet our overa ll ob jectives cou l d be f easible , and we will work with manufacturers as they develop thei r designs to help address any appropriate certification issues. Certification app r oval will be based on the ove ra ll ef f

ectiv eness o f the deterr ents. EPA will not m a ndate system s that comp romi se vehic l e perf o rm ance. One group of options focuses on prohibiting vehicle operation if reducing agent is not present. A “No-Engine Re start after Restart Countdown” approach allows a limited num b er of restarts once the redu cing agent ra nge reaches a certain mi ni mal lev e l of miles before the vehicle is unable to restart without the reducing agent tank being replenished. A “No-Start after Refueling” system has the ve h i cle unab l e to start after a refueling that has occurred and the reducing agent range is below a certain level (e.g. the typical range of

a single tank of f

u el). Lastly, a “ F uel-Locko u t” appro a c hhas the f u e l f ille r sys t e m lock out, preventing the user from be ing able to refuel the vehicle af ter th e reduc ing a g ent range drops below a certain level (e.g. the ty pical range of a single tank of fuel). The lockout m echanism would need to be robust, fo r example, not just a locked fuel door that can be pried open. System s such as these can all operate while som e reducing agent rem a ins in the storage tank, thus ensuring emi ssions controls during all vehicle operation tim es. Another way to m ake sure vehicle operator s are adding reducing agent when appropriate is to have vehicle perform a nce degraded in a m a nner that would be safe but would be onerous enough to discourage the user from operating the vehicle un til the reducing agent tank was ref illed. The key challenge of th is approach is to determine what would constitute anacceptable perform a nce degrad ationstrategy. A degradationapproach 6which m a intains vehicle or engine complia nce with the emissions requirem e nts helps address this concern. A ddition a lly, use of th is approach in c o m b ination with anothe r system could be m o re appropriate. 3) Identification of Incorrect Red u cing Agent. It is a l so imperative th at the SCR system design be able to detect incorrect redu cin g agent. Th e system mu st be ab le to identify and appropriately respond to a high NOx emissions perform a nce level associated with filling the storage tank with a fluid other than the m a nufa c ture r-sp ecif i ed redu cing agent, or with excessively diluted reducing ag ent. An exa mple woul d be filling the tank with water rather than the specified reduci ng agent (e.g., urea). Possible m echanis m s to address and imple m ent this concern in clude NOx sensors or urea sensors. We believe it is appropriate that the vehi cle respond in the sam e manner when incorrect reducing agent is detected as when the vehi cle runs low on reducing agent. Thus, once this cond itio n is recogn iz e d, the vehicle’s warning system would engage for a limited tim e before triggering the driver inducem ent (e.g., no-start, fuel lockout, perform a nce degradation, etc.) system

. This should allo w the operator time to refill the tank with proper reducing agent, or, in m o re serious instances, to obtain vehicle service. It is possible that reducin g agent quality and resulti ng SCR perform a nce m a y vary som e what. However, we believe that industry-w i de quality s p ecifications will largely address this issue. At th is tim e we do not be lieve it is n eces sary to requ ire SCR systems to identify slight differences in reducing agent quality. 4) Tamper Resistant D e sign. Manufacturers would have to dem onstrate to EPA that their SCR system design is tamp er resistant. There are three aspects of a d e sign th at w e would want to see m a de tamp er resistant:

• Warning System - The visual and audible components of the warning system should be as tamp er resistant as reasonably possible.
• The Driver I nducem ent Design - T a mp er resistant f eatur es will be ne ed ed to ensure that the driver inducem ent sy stem cannot be easily disabled. The specific req u irem ents will d e pend o n the driver inducem ent design. For example, the fuel door cannot be pried open for a fuel lockout system or the ability to start the vehicle with no reducing agent for a no-start design.
• The Reducing Agent Dosing System - Ensure that the dosing system cannot be easily deactivated, for example, by disconnecting the electrical connector to the dosing valve. 5) Durable Design. Manufacturers would have to dem onstrate to EPA that their SC R system design is durab le. This can b e accomp lished through the norm a l certification durability p r ocess. For light-duty v e h i cle s , this means a showing of comp liance over 120,000 miles, or 150,000 if m a nufa c turers choose to certify to the higher levels. Currently, o u r ligh t -du t y durability requirem e nts require dies el vehicles to undergo whole vehicle testing. Whole vehicle testing should ensure that the SCR catalyst, dosing system , reducing agent storage tank, and lines and hoses are durable

. For heavy-duty engines, the useful life is dependent on di fferentcl assi ficati o ns. For light heavy-duty diesel engines, the useful life is 110,000 mile s. For m e dium heavy- duty diesel engines, 7the useful life is 185,000 miles, and for heavy heavy-duty diesel engines, the useful lif e is 435,000 miles. At this tim e for heavy-duty e ngines we intend to ad dress the durability of the SCR s y stem comp onents when dete rioration factors ar e estab lished at certification.
B. Reducing Agent Availability and Accessibility The SCR system requires a reducing agent to function properly. Since vehicle operators will be resp onsible for refilling the reducing agent tank, it is imperative that the redu cing agent be readily available to consum ers. Sufficient and convenient availability of the reducing ag ent is essen t ial to m eet th ese objectives. Sufficient availability requires widespread distribution across the United Stat es. Convenient availability requires the reducing agent to be offered at locations th at are easy to find and that would occur during the vehicle operator’s norm al course of business or operation (e.g., commuting to work, going on vacation, transpo rting and deliv ering goods, and operation outside the scope of norm a l business hours). We believe that this can be be st achieved by relying on a com b ination of reducing agent availabil ity schem e s, som e of which are discussed below. W e believ e it is also important to ensure that SCR vehicle operators have opportunities to go beyond a specific OEM ne twork to obtain reducing agent. W e understand industry stakeholders are working on such broader availability m e chanisms and we enco urage th ese efforts. Approval criteria fo r manufacturer’s pl an fo r reducing agent availability and accessib i lity . EPA will re view a m a nufacturer’s plan for reducing agent availab ility and access i bility

. It is their responsibility to s how that reducing agent will be widely available and readily access i ble. EPA will in particularre view wh ethe r the following procedures are o r will be in place:
1. Reducing Agent Available at Dealerships

. The m a nufacturer s upp lies its de ale r s with the approp riate reducing agent and u s es best ef f

o rts to ensure that they will have adequate supplies to ensure that any and a ll of their custom ers who need the reducing agent will h a ve access to reducing agent with in a reason able tim e through the dealership.
2. Reducing Agent Available at Truckstops

. W e understand that heavy duty vehicles will rou tine l y ref u el and procure redu ctant at truc kstops and s i milar f acilities, rathe rth an at the m a nufactur er’ s dis tribu tor. Th eref ore, it will b e important f o r m a nuf a cturer s to dem onstrate either individually oras part of a collectiv e effort that it will b e reason able for truck operators to obtain re ductant at truckstops or othe r fueling locations when they stop to r e f u el. EPA’s re view will lo ok at th e ov erall inf r as tructure f o r th e particular class of vehicles.
3. Back-Up Plan

. The manufacturer provides a back- up plan, such as a toll-free phone num b er, that custom ers can call if they needreducing agent but ar e unable to obtain it from a dealership or other convenient source. The back-up plan n eeds to provide quick turn around, such as overnight delivery to th e consum er in response to a call to the tollfree num ber. 8Manufacturers should also be ab le to dem onstrate that reduc ing agent will be available at other comm ercial outlets. Such outlets wi ll be considered to be, but not limited to, fueling stations, quick oil change facilities, re pair and service f acilities, an d retail ou tle ts (e.g., autom o tive part stores and large retail stores). As the nu m b er of SCR-equipped diese l vehic l es grows, th e need f o r a ddition a l outlets will a l so incre a se. C. Education and Outreach for Po tential Owners and Service Industry SCR relies on the vehicle operator to periodi cally replen ish th e reduc ing a g ent to en su re the emission control system properly f unctions. T hus, it is incum b ent upon the m a nufacturer to educate potential ow ners about these requirem ents. W e believe m a nuf acture r s will n eed to develop and impl em ent an educat ion plan f o r prospective vehicle owners, dealership staff, includi ng sales and service personnel, afterm arket service facilities, fueling station staff, quick oil change faciliti es staff, retail staff, and any other groups or individuals that would be involved in the purchase or sales of SCRequipped vehicles, the service of SCR-equipped vehicles, or the sales of reducing agents (such as urea) to the public. The following ar e examples of t h e type of infor m ation EPA anticipates m a nufacturers would need to pr ovide to dem onstrate th eir pub lic edu catio n strategies:

• Explanation as to what an SCR system is, how it works, and why it is im portant that the redu cing agen t b e periodically replenished.
• What is the reducing agent used? Where does it go in the vehicle?
• W h ere can c onsum ers purchase the r e ducing agen t? How mu ch will it co st? Is it safe to handle?
• How often does the reducing agen t have to be replenished?
• How does the vehicle operator refill the reducing agent tank?
• Explain any potential odors associ ated with the reducing agent.
• Explain how the warning system s work.
• Explain consequences of ignoring warni ng system and not replenishing reducing agent.
• Other The following are examples of where the above infor m ation could be provided to the public :

• Owners m a nual
• Service m a nual
• Vehicle m e ssage cen ter
• Visor
• Fuel door or cap
• Reducing agent storage tank door or cap
• Comp any web site
• Dealersh ip b r ochures
• Sales agen t and service t echnician training m a nuals

9111. Additional Certification Issues A. Reducing; Agent Ouality Specifications Vehicle manufacturers should establish an industry-wide reducing agent quality standard and set specifications. In order to ensure proper operation, manufacturers will need to design SCR systems for the general range of commercially available reducing agents, thus showing the importance of having a defined set of reducing agent specifications. As with other parameters, EPA testing will be based on the same. It is also important that a common industry-wide reducing agent should be clearly and unambiguously identified, regardless of any brand name that is trademarked by a manufacturer. Similar to motor oils available today, consumers must be easily able to identify that the product they are purchasing can be used for their vehicle regardless of a brand name. An example of this is the American Petroleum Institute (API) “Staburst” logo used for motor oils.
B. Freeze Protection
The reducing agent should not be adversely affected by extreme climatic conditions, particularly freezing temperatures. Some reducing agents freeze at temperatures that occur seasonally in certain parts of the U.S. Urea, for example, freezes at 11°F. Manufacturers need to either use a reducing agent that will not freeze at low temperatures, or design their SCR system to prevent freezing (e.g., use of heater elements in or around the storage tank and heated lines). Manufacturers who use a heated SCR system need to ensure that minimal “thaw” time is required to melt enough reducing agent to recharge the system, should the reducing agent freeze due to extensive exposure to low temperatures. C. Reducing Agent Refilling Interval The reducing agent refilling interval will ultimately be determined by the manufacturer. EPA encourages manufacturers to adopt the longest interval reasonably possible. Since the refilling interval falls under allowable maintenance, the process for determining what would be an acceptable refilling interval for the reducing agent will be handled under the provision of 86.1834-0l(b)(7) for light duty and @36.094-25(b)(7) for heavy duty, as discussed above. 

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Acting Dir tor Compliance and Innovative Strategies Division

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