Office of Transportation

and Air Quality

EPA420-B-04-011

July 2004

Acceleration Simulation Mode

Test Procedures, Emission

Standards, Quality Control

Requirements, and Equipment

Specifications

Final Technical Guidance
EPA420-B-04-011

July 2004

Acceleration Simulation Mode Test Procedures,

 Emission Standards, Quality Control

Requirements, and Equipment Specifications

Final Technical Guidance

Certification and Compliance Division

Office of Transportation and Air Quality

U.S. Environmental Protection Agency

NOTICE

This Technical Report does not necessarily represent final EPA decisions or positions.

It is intended to present technical analysis of issues using data that are currently available.

The purpose in the release of such reports is to facilitate an exchange of

technical information and to inform the public of technical developments.
§85.1 §85.1 

§85.1 TEST STANDARDS AND CALCULATIONS.........................................................................................................3

(a) Emissions Standards......................................................................................................................................................3

(b) Test Score Calculation.................................................................................................................................................11

§85.2 TEST PROCEDURES ..............................................................................................................................................14

(a) General Requirements. ................................................................................................................................................14

(b) Vehicle Pre-Inspection and Preparation. .....................................................................................................................14

(c) Equipment Preparation and Settings. ..........................................................................................................................16

(d) Test Procedures. ..........................................................................................................................................................18

(e) Second Chance Tests...................................................................................................................................................24

§85.3 TEST EQUIPMENT SPECIFICATIONS ..............................................................................................................25

(a) Dynamometer Specifications.......................................................................................................................................25

(b) Emission Sampling System. ........................................................................................................................................32

(c) Analytical Instruments.................................................................................................................................................34

(d) Automated Test Process Software and Displays. ........................................................................................................38

§85.4 QUALITY CONTROL REQUIREMENTS ...........................................................................................................40

(a) General Requirements .................................................................................................................................................40

(b) Dynamometer ..............................................................................................................................................................40

(c) Emission Sampling System. ........................................................................................................................................45

(d) Analytic Instruments. ..................................................................................................................................................46

§85.5 TEST RECORD INFORMATION..........................................................................................................................54

(a) General Information. ...................................................................................................................................................54

(b) Ambient Test Conditions.............................................................................................................................................54

(c) ASM Mode or Modes..................................................................................................................................................54

(d) Diagnostic/Quality Assurance Information.................................................................................................................54

APPENDIX A: CALCULATING AUDIT TOLERANCES ................................................................................................56

Page 2 Test Standards and Calculations 
§85.1 §85.1 

§85.1 Test Standards and Calculations 

(a) Emissions Standards 

(1) Start-up ASM Standards 

Start-up standards should be used during the first cycle of the program. The exhaust 

emissions standards for the following model years and vehicle types are crossreferenced by the number in the column in §85.1(a)(4), as noted in the column 

headings: 

(i) Light Duty Vehicles. 

Model Years Hydrocarbons Carbon Monoxide 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) 

1996+ 1 21 

1991-1995 2 22 

1983-1990 4 23 

1981-1982 4 26 

1980 4 26 

1977-1979 11 30 

1975-1976 11 30 

1973-1974 13 34 

1968-1972 13 34 

(ii) High-Altitude Light Duty Vehicles. 

Model Years Hydrocarbons Carbon Monoxide 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) 

1983-1984 4 26 

1982 4 29 

Oxides of Nitrogen 

Table §85.1 (a)(4)(iii) 

41 

42 

43 

43 

48 

48 

50 

50 

51 

Oxides of Nitrogen 

Table §85.1 (a)(4)(iii) 

43 

43 

(iii) Light Duty Trucks 1 (less than 6000 pounds GVWR). 

Model Years Hydrocarbons Carbon Monoxide Oxides of Nitrogen 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) Table §85.1 (a)(4)(iii) 

1996+ 

<3750 LVW 1 21 41 

1996+ 

>3750 LVW 2 22 42 

1991-1995 5 26 43 

1988-1990 7 29 44 

1984-1987 7 29 49 

1979-1983 11 31 49 

1975-1978 12 32 50 

Page 3 Test Standards and Calculations 
§85.1 §85.1 

1973-1974 13 34 50 

1968-1972 13 34 51 

(iv) High-Altitude Light Duty Trucks 1 (less than 6000 pounds GVWR). 

Model Years Hydrocarbons Carbon Monoxide Oxides of Nitrogen 

Table §85.1 (a)(4)(i) Table §85.1 (a)(3)(ii) Table §85.1 (a)(4)(iii) 

1991+ 6 28 43 

1988-1990 9 30 44 

1984-1987 9 30 49 

1982-1983 12 33 49 

(v) Light Duty Trucks 2 (greater than 6000 pounds GVWR). 

Model Years Hydrocarbons Carbon Monoxide Oxides of Nitrogen 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) Table §85.1 (a)(4)(iii) 

1996+ 

<5750 LVW 2 22 42 

1996+ 

>5750 LVW 5 26 45 

1991-1995 5 26 46 

1988-1990 7 29 47 

1984-1987 7 29 49 

1979-1983 11 31 49 

1975-1978 12 32 50 

1973-1974 13 34 50 

1968-1972 13 34 51 

(vi) High-Altitude Light Duty Trucks 2 (greater than 6000 pounds GVWR). 

Model Years Hydrocarbons Carbon Monoxide Oxides of Nitrogen 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) Table §85.1 (a)(4)(iii) 

1991+ 6 28 46 

1988-1990 9 30 47 

1984-1987 9 30 49 

1982-1983 12 33 49 

(2) Original Final ASM Standards 

The following exhaust emissions standards are designed to achieve the emission 

reduction credits issued by EPA. They should only be used after at least one cycle of 

operation using the start-up standards in §85.1(a)(1). The exhaust emissions standards 

for the following model years and vehicle types are cross-referenced by the number in 

the column in §85.1(a)(4), as noted in the column headings. 

Revised Final Standards are provided in §85.1(a)(3) below. Use of these Revised Final 

Standards will provide the same emission reduction credits available as use of the 

Original Final ASM Standards. It is permissible to use combinations of the Original 

Page 4 Test Standards and Calculations 
§85.1 §85.1 

Final and Revised Final Standards, e.g. a state may implement the Original Final 

Standards for LDTs and the Revised Final Standards for LDVs. 

(i) Light Duty Vehicles. 

Model Years Hydrocarbons Carbon Monoxide 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) 

1996+ 

1983-1995 

1981-1982 

1980 

1977-1979 

1975-1976 

1973-1974 

1968-1972 

1 21 

1 21 

1 23 

1 23 

6 27 

6 27 

10 32 

10 32 

(ii) High-Altitude Light Duty Vehicles. 

Model Years Hydrocarbons Carbon Monoxide 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) 

1983-1984 2 23 

1982 2 23 

Oxides of Nitrogen 

Table §85.1 (a)(4)(iii) 

41 

41 

41 

45 

45 

48 

48 

49 

Oxides of Nitrogen 

Table §85.1 (a)(4)(iii) 

41 

41 

(iii) Light Duty Trucks 1 (less than 6000 pounds GVWR). 

Model Years Hydrocarbons Carbon Monoxide Oxides of Nitrogen 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) Table §85.1 (a)(4)(iii) 

1996+ 1 21 41 

1988-1995 3 24 42 

1984-1987 3 24 46 

1979-1983 8 28 46 

1975-1978 9 29 48 

1973-1974 10 32 48 

1968-1972 10 32 49 

(iv) High-Altitude Light Duty Trucks 1 (less than 6000 pounds GVWR). 

Model Years Hydrocarbons Carbon Monoxide Oxides of Nitrogen 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) Table §85.1 (a)(4)(iii) 

1988+ 4 26 42 

1984-1987 4 26 46 

1982-1983 9 30 46 

(v) Light Duty Trucks 2 (greater than 6000 pounds GVWR). 

Model Years Hydrocarbons Carbon Monoxide Oxides of Nitrogen 

Page 5 Test Standards and Calculations 
§85.1 §85.1 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) Table §85.1 (a)(4)(iii) 

1996+ 1 21 41 

1988-1995 3 24 44 

1984-1987 3 24 46 

1979-1983 8 28 46 

1975-1978 9 29 48 

1973-1974 10 32 48 

1968-1972 10 32 49 

(vi) High-Altitude Light Duty Trucks 2 (greater than 6000 pounds GVWR). 

Model Years Hydrocarbons Carbon Monoxide Oxides of Nitrogen 

Table §85.1 (a)(4)(i) Table §85.1 (a)(4)(ii) Table §85.1 (a)(4)(iii) 

1988+ 4 26 44 

1984-1987 4 26 46 

1982-1983 9 30 46 

(3) Revised Final ASM Standards 

The following exhaust emissions standards are designed to achieve the emission 

reduction credits issued by EPA. They should only be used after at least one cycle of 

operation using the start-up standards in §85.1(a)(1). The Revised Final Standards are 

of the form depicted below. 

Vehicle Engine Displacement (l) * Avg Emission <= Revised Standard* 

The Avg Emission is defined in §85.1(b)(1)(iv) and the vehicle shall pass the 

appropriate ASM test if the product of Engine Displacement and the respective Avg 

Emission is less than or equal to the Revised Standard for all three pollutants (HC, CO 

& NO). 

NOTE: The only exception to the form described above is for the ASM2525 LDT1 HC 

standards. In this one case, the standards listed for HC in 85.1(3)(iv) below, are to be 

compared directly to the Avg HC reading as defined in §85.1(b)(1)(iv). If the Avg HC 

measurement is less than the Revised Standard, the vehicle’s HC emissions are to 

receive a passing grade. This deviation from the procedure described above is only to 

be used for the HC ASM2525 LDT1 Revised Standards. 

It is permissible to use combinations of the Original Final and Revised Final Standards, 

e.g. a state may implement the Original Final Standards for LDTs and the Revised Final 

Standards for LDVs. 

*

 The units of the Revised Standard are (ppm * liter) for HC and NO and (%* liter) for CO. 

Page 6 Test Standards and Calculations 
§85.1 §85.1 

There are no High Altitude or Light Duty Truck 2 Revised Final Standards available at 

this time. 

(i) ASM5015 Light Duty Vehicles 

Pollutant MY Revised Standard 

HC 1980+ 275 

CO 1980-1982 1.3 

1983+ 1.1 

NO 1980 8,500 

1981+ 3,600 

(ii) ASM2525 Light Duty Vehicles 

Pollutant MY Revised Standard 

HC 1980-1989 500 

1990+ 300 

CO 1980-1982 2.3 

1983+ 1.6 

NO 1980 4,750 

1981+ 3,500 

(iii) ASM5015 Light Duty Trucks 1 (less than 6000 pounds GVWR) 

Pollutant MY Revised Standard 

HC 1980-1983 1140 

1984-1995 537 

1996+ 275 

CO 1980-1983 9.7 

1984-1995 5.4 

1996+ 1.1 

NO 1980-1987 14,145 

1988-1995 7,380 

1996+ 6,150 

(iv) ASM2525 Light Duty Trucks 1 (less than 6000 pounds GVWR) 

Pollutant MY Revised Standard 

HC* 1980-1983 340 

1984-1995 160 

1996+ 82 

CO 1980-1983 23.28 

1984-1995 12.96 

1996+ 4.4 

NO 1980-1987 32,200 

1988-1995 16,800 

1996+ 14,000 

*

 See NOTE above in §85.1(3) regarding the application of the HC ASM2525 LDT1 Revised Standards. 

Page 7 Test Standards and Calculations 
§85.1 §85.1

Page 8 Test Standards and Calculations

(4) ASM 2525 and 5015 Concentration Tables for Phase-In & Original Final Standards

(i) ASM2525 and ASM5015 Hydrocarbon (ppm C6) Table

Column # 1 10 10 11 11 12 12 13 13

ETW

5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525

1750 142 136 224 216 257 249 291 282 324 315 374 364 390 381 407 397 457 447 706 694 774 761 843 828 111 109

1875 134 129 212 205 243 236 275 266 306 297 353 344 368 359 384 375 431 421 665 653 729 717 794 780 105 103

2000 127 123 201 194 230 223 260 252 289 281 333 325 348 339 363 354 407 398 627 616 688 676 749 736 992 975

2125 121 116 191 184 219 212 246 239 274 267 316 308 329 321 343 335 385 376 592 582 650 638 707 695 938 921

2250 115 111 182 175 208 201 234 227 260 253 299 292 312 305 325 318 365 357 560 551 615 604 669 658 887 872

2375 109 106 173 167 198 192 223 216 247 241 284 277 297 290 309 302 346 339 531 522 583 573 635 624 841 827

2500 105 101 166 160 189 183 212 206 236 230 271 264 283 276 294 288 329 322 505 496 554 544 603 593 800 786

2625 100 97 159 153 181 175 203 197 225 219 259 252 270 263 281 274 314 307 481 472 528 518 574 564 761 748

2750 96 93 152 147 173 168 194 189 216 210 247 241 258 252 269 262 300 294 459 451 503 495 548 539 726 714

2875 92 89 146 141 167 161 187 181 207 201 237 231 247 241 257 251 287 281 439 431 481 473 524 515 695 683

3000 89 86 141 136 160 155 180 174 199 194 228 222 237 232 247 241 276 270 420 413 461 453 502 493 666 654

3125 86 83 136 132 155 150 173 168 191 186 219 214 228 223 238 232 265 260 404 397 443 435 482 474 639 628

3250 83 80 132 127 149 145 167 162 185 180 211 206 220 215 229 224 256 250 388 382 426 419 464 456 615 604

3375 81 78 128 123 145 140 162 157 179 174 204 199 213 208 221 216 247 241 374 368 411 404 447 440 593 583

3500 78 76 124 120 140 136 157 152 173 169 198 193 206 201 214 209 239 234 362 355 397 390 432 424 573 563

3625 76 74 120 117 136 132 152 148 168 164 192 187 200 195 207 203 231 226 350 344 384 377 418 411 554 544

3750 74 72 117 114 133 129 148 144 163 159 186 182 194 189 201 197 224 220 339 333 372 365 405 398 537 527

3875 72 70 114 111 129 125 144 140 159 155 181 177 188 184 196 191 218 213 329 323 361 355 393 386 521 512

4000 71 68 112 108 126 122 140 137 155 151 176 172 183 179 191 186 212 208 320 314 351 345 382 375 506 497

4125 69 67 109 106 123 119 137 133 151 147 172 168 179 175 186 181 206 202 311 305 341 335 371 365 492 484

4250 67 65 107 103 120 117 134 130 147 143 167 164 174 170 181 177 201 197 303 297 332 326 361 355 479 471

4375 66 64 104 101 118 114 131 127 144 140 164 160 170 166 177 173 196 192 295 290 323 318 352 346 467 459

4500 65 63 102 99 115 112 128 124 141 137 160 156 166 162 172 169 192 188 287 282 315 310 343 337 455 447

4625 63 61 100 97 113 109 125 122 137 134 156 152 162 159 169 165 187 183 280 275 308 302 335 329 444 436

4750 62 60 98 95 110 107 122 119 134 131 153 149 159 155 165 161 183 179 273 269 300 295 327 321 433 425

4875 61 59 96 93 108 105 120 117 132 128 149 146 155 152 161 157 179 175 267 262 293 288 319 313 423 415

5000 60 58 94 92 106 103 117 114 129 126 146 143 152 148 157 154 175 171 260 256 286 281 311 305 412 405

5125 58 57 93 90 104 101 115 112 126 123 143 139 148 145 154 150 171 167 254 250 279 274 304 298 402 395

5250 57 56 91 88 102 99 112 110 123 120 140 136 145 142 150 147 167 163 248 244 272 267 296 291 393 386

5375 56 55 89 86 100 97 110 107 121 118 137 133 142 139 147 144 163 159 242 238 266 261 289 284 383 376

5500 55 54 87 85 98 95 108 105 118 115 134 130 139 136 144 141 159 156 236 232 259 255 282 277 374 367

5625 54 53 86 83 96 93 106 103 116 113 131 128 136 133 141 138 156 152 231 226 253 248 276 271 365 359

5750 53 52 84 82 94 91 104 101 113 111 128 125 133 130 138 135 152 149 225 221 247 243 269 264 357 350

5875 52 51 83 80 92 90 102 99 111 108 125 122 130 127 135 132 149 146 220 216 241 237 263 258 348 342

6000 51 50 81 79 90 88 100 97 109 106 123 120 127 124 132 129 146 143 215 211 236 232 257 252 341 334

6125 50 49 80 78 89 86 98 95 107 104 120 118 125 122 129 126 143 140 210 206 231 227 251 247 333 327

6250 50 48 79 76 87 85 96 94 105 102 118 115 123 120 127 124 140 137 206 202 226 222 246 242 326 320

6375 49 48 77 75 86 84 95 92 103 101 116 113 120 118 125 122 138 135 202 198 222 218 242 237 320 314

6500 48 47 76 74 85 83 93 91 102 99 114 112 119 116 123 120 136 133 199 195 218 214 238 233 315 309

6625 48 46 76 74 84 82 92 90 101 98 113 110 117 114 121 119 134 131 196 192 215 211 234 230 310 304

6750 47 46 75 73 83 81 91 89 100 97 112 109 116 113 120 117 132 129 194 190 213 209 232 227 307 301

6875 47 46 75 73 83 81 91 89 99 97 111 109 115 113 119 117 132 129 193 189 211 207 230 225 305 299

7000 47 46 74 72 83 80 91 88 99 96 111 108 115 112 119 116 131 128 192 188 211 207 229 225 304 298

7125 47 46 74 72 82 80 90 88 98 96 111 108 115 112 119 116 131 128 192 188 211 206 229 225 304 298

7250 47 46 74 72 82 80 90 88 98 96 111 108 115 112 119 116 131 128 192 188 211 206 229 225 304 298

7375 47 46 74 72 82 80 90 88 98 96 111 108 115 112 119 116 131 128 192 188 211 206 229 225 304 298

7500 47 46 74 72 82 80 90 88 98 96 111 108 115 112 119 116 131 128 192 188 211 206 229 225 304 298

1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9
§85.1 §85.1

Page 9 Test Standards and Calculations

(ii) ASM2525 and ASM5015 Carbon Monoxide (%CO) Table

Column # 21 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 9 9 0 0 1 1 2 2 3 3 4 4

ETW

5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525

1750 0 80 0 77 1 26 1 22 1 64 1 83 2 02 2 43 2 21 2 73 2 78 3 64 2 97 3 94 3 16 4 24 3 54 4 85 3 92 5 45 4 31 6 06 5 07 7 26 5 26 7 44 8 02 9 90

1875 0 75 0 73 1 19 1 16 1 55 1 72 1 91 2 29 2 09 2 58 2 63 3 43 2 81 3 71 2 98 4 00 3 34 4 57 3 70 5 14 4 06 5 70 4 78 6 84 4 96 7 05 7 56 9 90

2000 0 71 0 69 1 13 1 09 1 47 1 63 1 81 2 17 1 97 2 43 2 48 3 24 2 65 3 51 2 82 3 77 3 16 4 31 3 49 4 85 3 83 5 38 4 51 6 45 4 68 6 68 7 14 9 90

2125 0 68 0 66 1 07 1 04 1 39 1 54 1 71 2 05 1 87 2 30 2 35 3 06 2 51 3 32 2 67 3 57 2 99 4 08 3 31 4 58 3 63 5 09 4 26 6 10 4 43 6 34 6 75 9 66

2250 0 64 0 62 1 02 0 99 1 32 1 47 1 62 1 94 1 77 2 18 2 23 2 90 2 38 3 14 2 53 3 38 2 83 3 86 3 13 4 34 3 44 4 82 4 04 5 78 4 20 6 00 6 40 9 14

2375 0 61 0 59 0 97 0 94 1 26 1 39 1 54 1 85 1 69 2 07 2 12 2 76 2 26 2 98 2 40 3 21 2 69 3 66 2 98 4 12 3 26 4 57 3 83 5 48 3 98 5 69 6 07 8 67

2500 0 59 0 57 0 93 0 90 1 20 1 33 1 47 1 76 1 61 1 97 2 02 2 62 2 15 2 84 2 29 3 05 2 56 3 48 2 83 3 91 3 10 4 35 3 65 5 21 3 79 5 41 5 78 8 25

2625 0 56 0 54 0 89 0 86 1 15 1 27 1 41 1 68 1 53 1 88 1 92 2 50 2 05 2 70 2 18 2 91 2 44 3 32 2 70 3 73 2 96 4 14 3 48 4 96 3 61 5 15 5 51 7 85

2750 0 54 0 52 0 85 0 82 1 10 1 21 1 34 1 60 1 47 1 80 1 84 2 39 1 96 2 58 2 09 2 78 2 33 3 17 2 58 3 56 2 83 3 95 3 32 4 73 3 45 4 92 5 26 7 50

2875 0 52 0 50 0 82 0 79 1 05 1 16 1 29 1 54 1 41 1 72 1 76 2 29 1 88 2 47 2 00 2 66 2 23 3 03 2 47 3 41 2 71 3 78 3 18 4 53 3 30 4 70 5 03 7 17

3000 0 50 0 48 0 79 0 76 1 01 1 12 1 24 1 48 1 35 1 66 1 69 2 19 1 80 2 37 1 92 2 55 2 14 2 91 2 37 3 27 2 60 3 62 3 05 4 34 3 17 4 51 4 83 6 87

3125 0 48 0 46 0 76 0 73 0 98 1 08 1 19 1 42 1 30 1 59 1 63 2 11 1 74 2 28 1 84 2 45 2 06 2 79 2 28 3 14 2 50 3 48 2 93 4 17 3 04 4 33 4 64 6 60

3250 0 46 0 45 0 73 0 71 0 94 1 04 1 15 1 37 1 26 1 53 1 57 2 03 1 67 2 20 1 78 2 36 1 99 2 69 2 20 3 02 2 40 3 35 2 82 4 01 2 93 4 17 4 47 6 35

3375 0 45 0 43 0 71 0 69 0 91 1 00 1 11 1 32 1 21 1 48 1 52 1 96 1 62 2 12 1 72 2 28 1 92 2 60 2 12 2 91 2 32 3 23 2 72 3 87 2 83 4 02 4 31 6 13

3500 0 44 0 42 0 69 0 67 0 88 0 97 1 08 1 28 1 17 1 43 1 47 1 89 1 56 2 05 1 66 2 20 1 86 2 51 2 05 2 82 2 24 3 12 2 63 3 74 2 73 3 88 4 17 5 92

3625 0 42 0 41 0 67 0 65 0 86 0 94 1 05 1 24 1 14 1 39 1 42 1 84 1 52 1 98 1 61 2 13 1 80 2 43 1 99 2 73 2 17 3 02 2 55 3 62 2 65 3 76 4 04 5 73

3750 0 41 0 40 0 65 0 63 0 83 0 92 1 02 1 20 1 11 1 35 1 38 1 78 1 47 1 92 1 56 2 07 1 74 2 36 1 93 2 64 2 11 2 93 2 47 3 51 2 57 3 64 3 91 5 55

3875 0 40 0 39 0 63 0 61 0 81 0 89 0 99 1 17 1 08 1 31 1 34 1 73 1 43 1 87 1 52 2 01 1 69 2 29 1 87 2 57 2 05 2 85 2 40 3 40 2 49 3 54 3 80 5 39

4000 0 39 0 38 0 62 0 60 0 79 0 87 0 96 1 14 1 05 1 28 1 31 1 68 1 39 1 82 1 48 1 95 1 65 2 22 1 82 2 49 1 99 2 77 2 33 3 31 2 43 3 44 3 70 5 24

4125 0 38 0 37 0 60 0 58 0 77 0 85 0 94 1 11 1 02 1 24 1 27 1 64 1 36 1 77 1 44 1 90 1 61 2 16 1 77 2 43 1 94 2 69 2 27 3 22 2 36 3 34 3 60 5 09

4250 0 37 0 36 0 59 0 57 0 75 0 83 0 92 1 08 1 00 1 21 1 24 1 60 1 32 1 72 1 40 1 85 1 56 2 11 1 73 2 36 1 89 2 62 2 21 3 13 2 30 3 25 3 51 4 96

4375 0 36 0 35 0 58 0 56 0 74 0 81 0 89 1 06 0 97 1 18 1 21 1 56 1 29 1 68 1 37 1 81 1 53 2 06 1 68 2 31 1 84 2 55 2 16 3 05 2 24 3 17 3 42 4 83

4500 0 36 0 35 0 57 0 55 0 72 0 79 0 87 1 03 0 95 1 16 1 18 1 52 1 26 1 64 1 34 1 76 1 49 2 01 1 64 2 25 1 80 2 49 2 11 2 98 2 19 3 09 3 34 4 71

4625 0 35 0 34 0 55 0 54 0 70 0 77 0 85 1 01 0 93 1 13 1 15 1 48 1 23 1 60 1 30 1 72 1 46 1 96 1 61 2 19 1 76 2 43 2 06 2 90 2 14 3 02 3 26 4 60

4750 0 34 0 33 0 54 0 53 0 69 0 76 0 84 0 99 0 91 1 10 1 13 1 45 1 20 1 57 1 28 1 68 1 42 1 91 1 57 2 14 1 72 2 37 2 01 2 83 2 09 2 95 3 18 4 49

4875 0 34 0 33 0 53 0 52 0 67 0 74 0 82 0 97 0 89 1 08 1 10 1 42 1 17 1 53 1 25 1 64 1 39 1 87 1 53 2 09 1 68 2 32 1 96 2 77 2 04 2 87 3 11 4 38

5000 0 33 0 32 0 52 0 51 0 66 0 73 0 80 0 95 0 87 1 05 1 08 1 38 1 15 1 49 1 22 1 60 1 36 1 82 1 50 2 04 1 64 2 26 1 92 2 70 1 99 2 81 3 03 4 28

5125 0 32 0 31 0 51 0 50 0 65 0 71 0 78 0 92 0 85 1 03 1 05 1 35 1 12 1 46 1 19 1 57 1 33 1 78 1 46 2 00 1 60 2 21 1 87 2 64 1 95 2 74 2 97 4 18

5250 0 32 0 31 0 50 0 49 0 63 0 70 0 77 0 90 0 83 1 01 1 03 1 32 1 10 1 43 1 16 1 53 1 30 1 74 1 43 1 95 1 56 2 16 1 83 2 58 1 90 2 68 2 90 4 08

5375 0 31 0 30 0 49 0 48 0 62 0 68 0 75 0 89 0 81 0 99 1 01 1 29 1 07 1 39 1 14 1 50 1 27 1 70 1 40 1 90 1 53 2 11 1 79 2 51 1 86 2 61 2 83 3 98

5500 0 30 0 30 0 48 0 47 0 61 0 67 0 73 0 87 0 80 0 97 0 99 1 26 1 05 1 36 1 11 1 46 1 24 1 66 1 37 1 86 1 49 2 06 1 75 2 46 1 82 2 55 2 77 3 89

5625 0 30 0 29 0 47 0 46 0 59 0 65 0 72 0 85 0 78 0 94 0 97 1 24 1 03 1 33 1 09 1 43 1 21 1 62 1 34 1 82 1 46 2 01 1 71 2 40 1 77 2 49 2 70 3 80

5750 0 29 0 29 0 46 0 45 0 58 0 64 0 70 0 83 0 76 0 92 0 94 1 21 1 01 1 30 1 07 1 40 1 19 1 59 1 31 1 78 1 43 1 96 1 67 2 34 1 74 2 43 2 64 3 71

5875 0 29 0 28 0 45 0 44 0 57 0 63 0 69 0 81 0 75 0 91 0 92 1 18 0 98 1 27 1 04 1 37 1 16 1 55 1 28 1 74 1 40 1 92 1 63 2 29 1 70 2 38 2 59 3 62

6000 0 28 0 28 0 44 0 44 0 56 0 62 0 67 0 80 0 73 0 89 0 91 1 16 0 96 1 25 1 02 1 34 1 14 1 52 1 25 1 70 1 37 1 88 1 60 2 24 1 66 2 33 2 53 3 54

6125 0 28 0 27 0 44 0 43 0 55 0 61 0 66 0 78 0 72 0 87 0 89 1 13 0 94 1 22 1 00 1 31 1 11 1 49 1 23 1 66 1 34 1 84 1 57 2 19 1 63 2 28 2 48 3 47

6250 0 27 0 27 0 43 0 42 0 54 0 60 0 65 0 77 0 71 0 85 0 87 1 11 0 93 1 20 0 98 1 28 1 09 1 46 1 20 1 63 1 31 1 80 1 54 2 15 1 60 2 23 2 43 3 40

6375 0 27 0 26 0 42 0 42 0 53 0 59 0 64 0 76 0 69 0 84 0 86 1 09 0 91 1 18 0 96 1 26 1 07 1 43 1 18 1 60 1 29 1 77 1 51 2 11 1 57 2 19 2 39 3 34

6500 0 26 0 26 0 42 0 41 0 52 0 58 0 63 0 74 0 68 0 83 0 84 1 08 0 90 1 16 0 95 1 24 1 06 1 41 1 16 1 57 1 27 1 74 1 48 2 07 1 54 2 15 2 35 3 28

6625 0 26 0 26 0 41 0 41 0 52 0 57 0 62 0 73 0 67 0 82 0 83 1 06 0 88 1 14 0 94 1 23 1 04 1 39 1 15 1 55 1 25 1 72 1 46 2 04 1 52 2 12 2 32 3 23

6750 0 26 0 26 0 41 0 41 0 51 0 57 0 61 0 73 0 67 0 81 0 82 1 05 0 88 1 13 0 93 1 21 1 03 1 37 1 14 1 54 1 24 1 70 1 45 2 02 1 50 2 10 2 29 3 20

6875 0 26 0 25 0 40 0 40 0 51 0 56 0 61 0 72 0 66 0 80 0 82 1 04 0 87 1 12 0 92 1 20 1 02 1 36 1 13 1 52 1 23 1 68 1 44 2 00 1 49 2 08 2 28 3 17

7000 0 25 0 25 0 40 0 40 0 51 0 56 0 61 0 72 0 66 0 80 0 82 1 04 0 87 1 12 0 92 1 20 1 02 1 36 1 12 1 52 1 23 1 68 1 43 2 00 1 49 2 08 2 27 3 17

7125 0 25 0 25 0 40 0 40 0 51 0 56 0 61 0 72 0 66 0 80 0 81 1 04 0 87 1 12 0 92 1 20 1 02 1 36 1 12 1 52 1 22 1 68 1 43 2 00 1 49 2 08 2 27 3 17

7250 0 25 0 25 0 40 0 40 0 50 0 56 0 61 0 72 0 66 0 80 0 81 1 04 0 86 1 12 0 92 1 20 1 02 1 36 1 12 1 52 1 22 1 68 1 43 2 00 1 49 2 08 2 27 3 17

7375 0 25 0 25 0 40 0 40 0 50 0 56 0 61 0 72 0 66 0 80 0 81 1 04 0 86 1 12 0 92 1 20 1 02 1 36 1 12 1 52 1 22 1 68 1 43 2 00 1 49 2 08 2 27 3 17

7500 0 25 0 25 0 40 0 40 0 50 0 56 0 61 0 72 0 66 0 80 0 81 1 04 0 86 1 12 0 92 1 20 1 02 1 36 1 12 1 52 1 22 1 68 1 43 2 00 1 49 2 08 2 27 3 17

2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 3 3 3 3 3 3 3
§85.1 §85.1

Page 10 Test Standards and Calculations

(iii) ASM2525 and ASM5015 Nitric Oxide (ppm NO) Table

Column # 41 41 42 42 43 43 44 44 45 45 46 46 47 47 48 48 49 49 50 50 51 51

ETW 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525 5015 2525

1750 1212 1095 1819 1642 2272 2114 2725 2587 3178 3060 3631 3532 4084 4005 4990 4950 4990 4960 4990 4980 4990 4990

1875 1142 1031 1713 1547 2181 1991 2649 2435 3117 2879 3586 3323 4054 3767 4990 4655 4990 4738 4990 4906 4990 4990

2000 1077 973 1616 1460 2058 1877 2499 2295 2941 2713 3383 3131 3824 3548 4707 4384 4778 4535 4919 4838 4990 4990

2125 1018 920 1527 1380 1944 1774 2360 2167 2776 2561 3192 2955 3609 3348 4441 4136 4578 4349 4853 4776 4990 4990

2250 964 871 1446 1307 1839 1678 2232 2050 2625 2422 3018 2794 3411 3165 4197 3909 4395 4179 4792 4720 4990 4990

2375 915 827 1372 1240 1744 1592 2115 1943 2487 2295 2859 2646 3231 2998 3974 3701 4228 4024 4736 4668 4990 4990

2500 869 786 1304 1179 1657 1512 2009 1845 2361 2179 2714 2512 3066 2845 3771 3512 4076 3881 4685 4620 4990 4990

2625 828 749 1242 1123 1577 1440 1912 1756 2246 2073 2581 2389 2916 2706 3585 3339 3936 3752 4639 4577 4990 4990

2750 791 715 1186 1072 1504 1374 1823 1675 2142 1976 2460 2277 2779 2579 3416 3181 3809 3579 4596 4374 4990 4772

2875 756 684 1134 1026 1438 1313 1742 1601 2046 1888 2350 2175 2654 2463 3261 3037 3669 3417 4484 4176 4892 4556

3000 725 656 1088 984 1378 1258 1668 1533 1959 1808 2249 2082 2539 2357 3120 2906 3510 3270 4290 3996 4680 4359

3125 696 630 1045 945 1323 1208 1601 1471 1879 1734 2157 1997 2435 2260 2992 2787 3366 3135 4114 3832 4488 4180

3250 670 607 1006 910 1273 1163 1539 1415 1806 1667 2073 1920 2340 2172 2874 2677 3234 3012 3952 3681 4311 4016

3375 647 585 970 878 1227 1121 1483 1363 1740 1606 1997 1849 2253 2092 2767 2577 3113 2899 3804 3544 4150 3866

3500 625 566 937 848 1184 1082 1432 1316 1679 1550 1926 1784 2174 2018 2668 2486 3002 2796 3669 3418 4002 3728

3625 605 547 907 821 1146 1047 1384 1273 1623 1498 1862 1724 2100 1950 2578 2401 2900 2701 3544 3302 3867 3602

3750 586 531 879 796 1110 1014 1340 1233 1571 1451 1802 1669 2033 1887 2494 2323 2806 2614 3429 3195 3741 3485

3875 569 515 853 773 1077 984 1300 1195 1523 1407 1747 1618 1970 1829 2417 2251 2719 2533 3323 3096 3625 3377

4000 553 501 829 751 1046 956 1262 1161 1479 1365 1695 1570 1912 1775 2345 2184 2638 2457 3224 3003 3517 3276

4125 538 487 807 731 1017 930 1227 1128 1437 1327 1647 1526 1857 1724 2277 2122 2562 2387 3131 2917 3416 3182

4250 524 475 786 712 990 905 1194 1098 1398 1291 1602 1484 1806 1677 2214 2063 2490 2320 3044 2836 3321 3094

4375 510 463 766 694 964 882 1162 1069 1360 1257 1559 1444 1757 1632 2154 2007 2423 2258 2961 2759 3230 3010

4500 498 451 747 677 939 859 1132 1042 1325 1224 1518 1406 1711 1589 2096 1953 2359 2198 2883 2686 3145 2930

4625 486 440 728 661 916 838 1104 1015 1291 1193 1479 1370 1666 1548 2042 1903 2297 2140 2807 2616 3063 2854

4750 474 430 711 645 893 818 1076 990 1259 1163 1441 1336 1624 1508 1989 1854 2238 2085 2735 2549 2983 2780

4875 463 420 694 630 872 798 1049 966 1227 1134 1405 1302 1583 1470 1938 1806 2180 2032 2665 2483 2907 2709

5000 452 410 677 615 850 778 1023 942 1196 1106 1369 1269 1542 1433 1889 1760 2125 1980 2597 2420 2833 2640

5125 441 400 661 600 830 760 998 919 1167 1078 1335 1237 1503 1397 1840 1715 2070 1930 2530 2359 2760 2573

5250 431 391 646 586 810 741 974 896 1138 1051 1301 1206 1465 1362 1793 1672 2017 1881 2466 2298 2690 2507

5375 420 382 631 573 790 723 950 874 1109 1025 1269 1176 1428 1327 1747 1629 1966 1833 2403 2240 2621 2443

5500 410 373 616 559 771 706 926 853 1082 1000 1237 1147 1392 1294 1703 1587 1916 1786 2341 2183 2554 2381

5625 401 364 601 546 752 689 904 832 1055 975 1206 1118 1357 1261 1659 1547 1867 1740 2282 2127 2489 2321

5750 391 356 587 534 734 673 882 812 1029 951 1176 1090 1323 1230 1617 1508 1820 1697 2224 2074 2426 2262

5875 383 348 574 522 717 657 860 793 1004 928 1147 1064 1290 1199 1577 1471 1774 1654 2168 2022 2366 2206

6000 374 340 561 510 701 642 840 774 980 906 1120 1039 1259 1171 1539 1435 1731 1614 2116 1973 2308 2152

6125 366 333 549 499 685 628 822 757 958 886 1094 1015 1230 1144 1503 1401 1690 1577 2066 1927 2254 2102

6250 359 326 538 489 671 615 804 741 937 867 1070 993 1203 1119 1469 1371 1653 1542 2020 1884 2204 2056

6375 352 320 528 480 658 604 788 727 919 850 1049 973 1179 1096 1439 1343 1619 1510 1979 1846 2159 2014

6500 346 315 519 473 647 593 775 714 902 835 1030 956 1158 1077 1413 1318 1590 1483 1943 1813 2119 1977

6625 341 311 512 466 638 585 763 704 889 823 1014 941 1140 1060 1391 1298 1565 1460 1913 1785 2087 1947

6750 338 307 507 461 631 578 755 696 879 813 1003 931 1127 1048 1374 1283 1546 1443 1890 1764 2062 1924

6875 335 305 503 458 626 574 749 691 872 807 995 924 1118 1040 1364 1273 1534 1432 1875 1750 2046 1909

7000 335 305 502 457 624 573 747 689 870 805 992 921 1115 1037 1360 1269 1530 1428 1870 1745 2040 1904

7125 335 305 502 457 625 573 747 689 870 805 992 921 1115 1037 1360 1269 1531 1428 1874 1745 2045 1904

7250 335 305 502 457 625 573 747 689 870 805 992 921 1115 1037 1360 1269 1531 1428 1874 1745 2045 1904

7375 335 305 502 457 625 573 747 689 870 805 992 921 1115 1037 1360 1269 1531 1428 1874 1745 2045 1904

7500 335 305 502 457 625 573 747 689 870 805 992 921 1115 1037 1360 1269 1531 1428 1874 1745 2045 1904
§85.1 §85.1 

(b) Test Score Calculation 

(1) Exhaust Gas Measurement Calculation. 

(i) Measurement Start. The analysis and recording of exhaust gas concentrations 

shall begin 15 seconds after the applicable test mode begins, or sooner if the 

system response time (to 95% of full scale) is less than 15 seconds. The 

analysis and recording of exhaust gas concentrations shall not begin sooner than 

the time period equivalent to the response time of the slowest transducer. 

(ii) Sample Rate. Exhaust gas concentrations shall be analyzed at a minimum rate 

of once per second. 

(iii) Negative Values. Negative concentration readings shall be integrated as zero 

and recorded as such. 

(iv) Emission Measurement Calculations. Partial stream (concentration) emissions 

shall be calculated based on a running 10 second average. The values used for 

HC(j), CO(j), and NO(j) are the raw (uncorrected) tailpipe concentrations. 

10 

∑ HC(j)*DCF(j) 

(A) AvgHC = j=1 

10 

10 

∑CO(j) * DCF(j) 

(B) AvgCO = 

j=1 

10 

10 

∑ NO(j)*DCF(j) 

(C) AvgNO = j=1

10 

* Kh 

(v) Dilution Correction Factor. The analyzer software shall multiply the raw 

emissions values by the Dilution Correction Factor (DCF) during any valid 

ASM emissions test. The DCF accounts for exhaust sample dilution (either 

intentional or unintentional) during an emissions test. The analyzer software 

shall calculate the DCF using the following procedure, and shall select the 

appropriate vehicle fuel formula. If the calculated DCF exceeds 3.0 then a 

default value of 3.0 shall be used. 

[CO2 ]measured (A) X = 

[CO2 ]measured + [CO]measured 

Page 11 Test Standards and Calculations 
§85.1 §85.1 

Where [CO2]measured and [CO]measured are the instantaneous ASM 

emissions test readings. 

(B) Calculate [CO2]adjusted using the following formulas. 

(1) 

(2) 

(3) 

(4) 

For Gasoline: 

X [CO2 ]adjusted = *100

4.644 + 1.88X 

For Methanol or Ethanol: 

X [CO *100 2 ]adjusted = 

4.73 + 1.88X 

For Compressed Natural Gas (CNG): 

X [CO *100 2 ]adjusted = 

6.64 + 1.88X 

For Liquid Propane Gas (LPG): 

X [CO *100 2 ]adjusted = 

5.39 + 1.88X 

(C) Calculate the DCF using the following formula: 

DCF = 

[CO2 ]adjusted 

[CO2 ]measured 

(vi) NO Humidity Correction Factor. The NO measurement shall be adjusted based 

on relative humidity using a correction factor Kh, calculated as follows: 

(A) Standard Method 

1 Kh = 

1.0 - 0.0047(H - 75) 

Where: 

H = Absolute humidity in grains of water per pound of dry air. 

(43.478)R a * Pd

= 

PB - (Pd *Ra /100) 

Ra = Relative humidity of the ambient air, percent. 

Page 12 Test Standards and Calculations 
§85.1 §85.1 

Pd = Saturated vapor pressure, mm Hg at the ambient dry bulb

* temperature . 

= (-4.14438*10-3) + (5.76645*10-3 * Td) – (6.32788*10-5 * 

Td

2

) + (2.12294*10-6 * Td

3

) – (7.85415*10-9 * Td

4

) + 

(6.55263*10-11

 * Td

5

) 

Where:Td = Dry bulb temperature, °F 

PB = Barometric pressure, mm Hg. 

(B) Revised method• 

Kh = e

[0.004977(H−75)−0.004447(T−75)] 

Where: H =Absolute humidity in grains of water per pound 

of dry air. 

T =Temperature in °F. 

NOTE: If the calculated KH using either method of calculation is greater 

than 2.19, the value of KH shall be set at 2.19. 

(2) Pass/Fail Determination. 

A pass or fail determination shall be made for each applicable test mode based on a 

comparison of the applicable test standards and the measured value for HC, CO, and 

NO as described in §85.1(b)(1)(iv). A vehicle shall pass the test mode if the emission 

values for HC, CO, and NO are simultaneously below or equal to the applicable short 

test standards for all three pollutants. A vehicle shall fail the test mode if the values for 

HC, CO, or NO, or any combination of the three, are above the applicable standards at 

the expiration of the test time. 

*

 SAEJ1094, §6.1.1.3, p.38, June 1992. This equation is a least squares fit to the Keenan and Keyes "steam table." It 

reproduces steam table values within 0.0001 in Hg for temperatures from 20° to 110°F. 

•

 This revised method for calculating Kh as a function of both T and H is based on work performed by Sierra Research under 

contract 68-C4-0056, Work Assignment 2-04. If the calculated value of Kh exceeds 2.19, the value of Kh shall be set to 2.19. 

This analysis used the same MY69, 5-vehicle sample employed for the original Kh factor study that resulted in the current 

CFR standard Kh calculation method (listed in (vi)(F) above). However, in many cases IM testing occurs outside the 

temperature limits set by the CFR for the standard method; therefore, at this time EPA recommends using the revised method 

when testing above 86°F. The new method makes the calculation of Kh more accurate over a wider range of temperatures. 

Page 13 Test Standards and Calculations 
§85.2 §85.2 

§85.2 Test Procedures 

(a) General Requirements. 

(1) Vehicle Characterization. The following information shall be determined for the vehicle 

being tested and used to automatically select the dynamometer power absorption settings: 

(i) Vehicle type: LDGV, LDGT1, LDGT2, HDGT, and others as needed 

(ii) Chassis model year 

(iii) Make 

(iv) Model 

(v) Number of cylinders 

(vi) Cubic inch or liters displacement of the engine 

(vii) Transmission type 

(viii) Equivalent Test Weight. 

(2) Ambient Conditions. The ambient temperature, absolute humidity, and barometric 

pressure shall be recorded continuously during the test cycle or as a single set of readings 

up to 4 minutes before the start of the driving cycle. 

(3) Restart. If shut off, the vehicle shall be restarted as soon as possible before the test and 

shall be running for at least 30 seconds prior to the start of the ASM driving cycle. 

(4) Void Test Conditions. The test shall immediately end and any exhaust gas measurements 

shall be voided if the instantaneous measured concentration of CO plus CO2 falls below 

six percent or the vehicle's engine stalls at any time during the test sequence. 

(5) Vehicle Brakes. The vehicle's brakes shall not be applied during the test modes. If the 

vehicle’s brakes are applied during testing the mode timer shall be reset to zero (tt = 0). 

Some dynamometers do not have the ability to automatically sense if a vehicle’s brakes 

become engaged. In these instances, it shall be the responsibility of the Program to 

implement technician training and test procedures so that a test shall be manually 

restarted if the vehicle’s brakes are applied. 

(6) Test Termination. The test shall be aborted or terminated upon reaching the overall 

maximum test time. 

(b) Vehicle Pre-Inspection and Preparation. 

(1) Accessories. All accessories (air conditioning, heat, defogger, radio, automatic traction 

control if switchable, etc.) shall be turned off (if necessary, by the inspector). 

(2) Traction Control and Four-Wheel Drive (AWD). Most vehicles with traction control 

can be tested on AWD dynamometers; however, this is not true for all vehicles and 

dynamometer models. 

Page 14 7/28/04 Test Procedures 
§85.2 §85.2 

Vehicles with traction control systems that cannot be turned off shall not be tested on 

two wheel drive dynamometers. Vehicles with AWD that cannot be turned off shall 

only be tested on AWD dynamometers. If the AWD function can be disabled, then 

AWD vehicles may be tested on two wheel drive dynamometers. 

It is the responsibility of all vehicle OEMs to notify the Certification and Compliance 

Division of EPA in writing of any vehicles that can't be tested on AWD dynamometers 

so that EPA may share this information with state IM programs. 

(c) Exhaust Leaks. The vehicle shall be inspected for exhaust leaks. Audio assessment 

while blocking exhaust flow, or gas measurement of carbon dioxide or other gases shall 

be acceptable. Vehicles with leaking exhaust systems shall be rejected from testing. 

(4) Fluid Leaks. The vehicle shall be inspected for fluid leaks. Vehicles with leaking 

engine oil, transmission fluid, or coolant shall be rejected from testing. 

(5) Mechanical Condition. Vehicles with obvious mechanical problems (engine, 

transmission, brakes, or exhaust) that either create a safety hazard or could bias test 

results shall be rejected from testing. 

(6) Operating Temperature. The vehicle shall be at normal operating temperature prior to 

the start of the test. The vehicle temperature gauge, if equipped and operating, shall be 

checked to assess temperature. Vehicles in overheated condition shall be rejected from 

testing. 

(7) Tire Condition. Vehicles shall be rejected from testing if tread indicators, tire cords, 

bubbles, cuts, or other damage are visible. Vehicles shall be rejected from testing if 

they have space-saver spare tires or if they do not have reasonably sized tires on the 

drive axle or axles. Vehicles may be rejected if they have different sized tires on the 

drive axle or axles. In test-and-repair facilities, drive wheel tires shall be checked with 

a gauge for adequate tire pressure. In test-only facilities, drive wheel tires shall be 

visually checked for adequate pressure level. Drive wheel tires that appear low shall be 

inflated to approximately 30 psi, or to tire sidewall pressure, or vehicle manufacturer's 

recommendation. Alternatively, vehicles with apparent low tire pressure may be 

rejected from testing. 

(8) Gear Selection. The vehicle shall be operated during each mode of the test with the 

gear selector in drive for automatic transmissions and in second (or third if more 

appropriate) for manual transmissions for the loaded modes. 

(9) Roll Rotation. The vehicle shall be maneuvered onto the dynamometer with the drive 

wheels positioned on the dynamometer rolls. Prior to test initiation, the rolls shall be 

rotated until the vehicle laterally stabilizes on the dynamometer. Vehicles that cannot 

be stabilized on the dynamometer shall be rejected from testing. Drive wheel tires shall 

be dried if necessary to prevent slippage. 

(10) Vehicle Restraint. Testing shall not begin until the vehicle is restrained. Any restraint 

system shall meet the requirements of §85.3(a)(5)(ii). In addition, the parking brake 

shall be set for front wheel drive vehicles prior to the start of the test, unless parking 

brake functions on front axle or if is automatically disengaged when in gear. 

Page 15 Test Procedures 
§85.2 §85.2 

(11) Vehicle Conditioning. 

(i) Queuing Time. When a vehicle waits in a queue more than 20 minutes or when 

a vehicle is shut-off for more than 5 minutes prior to the test, vehicle 

conditioning shall be performed for 60 seconds, as specified in 

§85.2(b)(12)(ii)(C) below. This 60 second period is in addition to the test times 

described in §85.2(d). Emissions may be monitored during this cycle and if 

passing readings are obtained, as specified for the ASM cycle in §85.2(d), then 

the cycle may be terminated and the respective ASM mode skipped. 

(ii) Discretionary Preconditioning. At the program's discretion, any vehicle may be 

preconditioned using any of the following methods: 

(A) Non-loaded Preconditioning. Increase engine speed to approximately 

2500 RPM, for up to 4 minutes, with or without a tachometer. 

(B) Loaded Preconditioning. Drive the vehicle on the dynamometer at 30 

miles per hour for up to 240 seconds at road-load. 

(C) ASM Preconditioning. Drive the vehicle on the dynamometer using 

either mode of the ASM test as specified in §85.2(d). 

(D) Transient Preconditioning. After maneuvering the vehicle onto the 

dynamometer, drive a transient cycle consisting of speed, time, 

acceleration, and load relationships such as the IM240. 

(c) Equipment Preparation and Settings. 

(1) Analyzer Warm-Up. Emission testing shall be locked out until the analyzer is warmedup and stable. The analyzer shall reach stability within 30 minutes from startup. If an 

analyzer does not achieve stability within the allotted time frame, it shall remain locked 

out from testing. The instrument shall be considered "warmed-up" when the zero and 

span readings for HC, CO, NO, and CO2 have stabilized within the accuracy values 

specified in §85.3(c)(3)(vi) for five minutes without adjustment. 

(2) Emission Sample System Purge. While the equipment is in operation, the sample 

system shall be continuously purged after each test for at least 15 minutes if not taking 

measurements. If the equipment has been shut down, the system shall be purged for 5 

minutes or until the HC reading is less than 15 ppm C6 prior to the start of a test. 

(3) Probe Insertion. The sample probe shall be inserted into the vehicle's tailpipe to a 

minimum depth of 10 inches. If the vehicle's exhaust system prevents insertion to this 

depth, a tailpipe extension shall be used. 

Page 16 Test Procedures 
§85.2 §85.2 

(4) Multiple exhaust pipes. Exhaust gas concentrations from vehicle engines equipped 

with functionally independent multiple exhaust pipes shall be sampled simultaneously. 

The collection system shall be designed such that the flow through both probes is 

within ± 10%. 

(5) Analyzer Preparation. The analyzer shall perform an automatic zero, an ambient air 

reading, and an HC hang-up check prior to each test. This process shall occur within 

two minutes of the start of the test. 

(i) Automatic Gas Zero. The analyzer shall conduct automatic zero adjustments 

using the zero gas specified in §85.4(d)(2)(iii). The zero adjustment shall 

include the HC, CO, CO2, and NO channels. Bottled or generated zero air may 

be used. 

(ii) Ambient Air Reading. Filtered ambient air shall be introduced to the analyzer 

before the sample pump, but after the sample probe, hose, and filter/water trap. 

The analyzer shall record the concentrations of the four measured gases, but 

shall make no adjustments. 

(1) The sample through probe has less than 15 ppm HC, 0.02% CO, and 

25 ppm NO. 

(iii) HC Hang-up Determination. The analyzer shall sample ambient air through the 

probe to determine background pollution levels and HC hang-up. The analyzer 

shall be locked out from testing until: 

(1) The residual HC in the sampling system (probe sample - ambient air 

reading) is less than 7 ppm. 

(6) Cooling System. When ambient temperatures exceed 72°F, testing shall not begin until 

the cooling system blower is positioned and activated. The cooling system shall be 

positioned to direct air to the vehicle cooling system, but shall not be directed at the 

catalytic converter. The use of a cooling system is optional when testing at 

temperatures below 50EF. If a cooling system is in use, testing shall not begin until the 

cooling system is positioned and activated. Furthermore, the hood may be opened at 

the state's discretion. 

(7) Dynamometer Warm-Up. Dynamometers that do not have temperature compensation 

shall be automatically warmed-up prior to official testing and shall be locked out until 

warmed-up. Dynamometers resting (not operated for at least 30 seconds and at least 15 

mph) for more than 30 minutes shall pass the coast-down check specified in §85.4(b)(1) 

prior to use in testing. As specified in §85.4(a)(2), control charts may be used to 

demonstrate allowing a longer duration of inactivity before a required warm-up. 

If the dynamometer is not warmed-up as outlined above, then the parasitic losses, 

typically bearing and windage friction expressed as a function of velocity, shall be 

characterized as a function of bearing temperature or some alternative parameter that 

the manufacturer ca demonstrate is correlated with parasitic losses. Based on this 

characterization, the dynamometer load shall be automatically adjusted to compensate 

Page 17 Test Procedures 
§85.2 §85.2 

for changes in parasitic losses as a function of dynamometer temperature in order to 

ensure dynamometer load accuracy without having to perform dynamometer warm-ups. 

All-wheel-drive dynamometers must characterize losses for the entire system, i.e. both 

roll sets. If an all-wheel-drive dynamometer can be operated in either two- or allwheel-drive mode, parasitic losses must be characterized in both two- and all-wheeldrive modes. System software shall automatically change parasitic losses depending on 

how the vehicle is tested. 

(8) Dynamometer Settings. Dynamometer power absorption and inertia weight settings 

shall be automatically chosen from an EPA-supplied or EPA-approved electronic lookup table which will be referenced based upon the vehicle identification information 

obtained in §85.2(a)(1)*

. Vehicles not listed shall be tested using default power 

absorption and inertia settings in the latest version of the EPA I/M Look-up Table, as 

posted on EPA's web site: www.epa.gov/orcdizux/im.htm. At a minimum the look-up 

table on the ASM host computer should be updated once per year. 

(9) Engine Speed. Engine speed measurement equipment shall be attached on all 1996 and 

newer light duty vehicles and trucks, and in test-and-repair programs, engine speed 

shall also be monitored on all pre-1996 vehicles. On vehicles equipped with OBD 

systems (1996 and newer), it is recommended that the SAE-standardized OBD plug be 

used. Engine speed measurement equipment shall meet the requirements of 

§85.3(c)(5). 

(d) Test Procedures. 

The test sequence shall consist of either a single ASM mode or both ASM modes described in 

§85.2(d)(1) and (2), and may be performed in either order (with appropriate change in 

transition requirements in §85.2(d)(1)(iv)). Vehicles that fail the first-chance test described in 

§85.2(d) shall receive a second-chance test if the conditions in §85.2(e) apply. An Alternative 

ASM mode is described in §85.2(d)(3). This new procedure was designed to improve vehicle 

throughput by reducing the likelihood of failing a vehicle because it had locked into a nonrepresentative high emitting mode of operation. Vehicles that fail the Alternative ASM Test 

Procedure may be granted a second-chance test at the state’s discretion. 

The test timer shall start (tt=0) when the conditions specified in §85.2(b) and §85.2(c) are met 

and the mode timer initiates as specified in §85.2(d)(1), §85.2(d)(2), or §85.2(d)(3). Maximum 

test times for various test scenarios are described in §85.2 (e)(1) below. The test shall be 

immediately terminated or aborted upon reaching the overall maximum test time. 

* EPA last updated the look-up table on September 10, 1998 (I/M LOOK-UP TABLE, RELEASE 1.6.1). Since that time the 

table has been updated by states, contractors and consulting firms. 

Page 18 Test Procedures 
§85.2 §85.2 

(1) ASM5015 Mode. 

(i) The mode timer shall start (mt=0) when the dynamometer speed (and 

corresponding power) is maintained within 15±1.0 miles per hour for 5 

continuous seconds. The dynamometer shall apply the constant torque over the 

duration of the ASM mode. Torque shall be set to the correct torque necessary 

to generate the required horsepower at 15.0 mph. If actual torque applied 

deviates by more than 2% from the target torque for more than two consecutive 

seconds, the test mode timer shall be set to mt=0. 

(ii) The dynamometer power shall be automatically selected from an EPA-supplied 

or EPA-approved look-up table, based upon the vehicle identification 

information described in §85.2(a)(1). If a vehicle is not specifically listed in the 

EPA-approved table, default values from the same table shall be used. If an 

appropriate default value is not available in the EPA-approved table, ASM 

loading should be taken from the following table: 

Default ASM5015 Actual Horsepower Settings 

For 8.6" Dynamometers HP50158 

Vehicle Type 

Number of Cylinders 

3 4 5 & 6 8 > 8 

Sedans 

Station Wagons 

Mini-vans 

Pickup Trucks 

Sport/Utility 

Full Vans 

7.9 

8.1 

10.2 

9.6 

10.1 

10.3 

11.4 

11.7 

14.1 

13.1 

13.4 

13.9 

13.8 

13.8 

15.8 

16.4 

15.5 

17.7 

16.4 

16.1 

17.9 

19.2 

19.4 

19.6 

16.0 

16.1 

18.2 

21.1 

21.1 

20.5 

Default ASM5015 Actual Horsepower Settings 

For 20" Dynamometers HP501520 

Vehicle Type 

Number of Cylinders 

3 4 5 & 6 8 > 8 

Sedans 

Station Wagons 

Mini-vans 

Pickup Trucks 

Sport/Utility 

Full Vans 

8.1 

8.3 

10.4 

9.8 

10.5 

10.8 

11.8 

12.1 

14.5 

13.4 

13.8 

14.4 

14.3 

14.2 

16.3 

16.8 

15.9 

18.2 

16.9 

16.6 

18.5 

19.8 

19.9 

20.2 

16.6 

16.6 

18.7 

21.7 

21.7 

21.1 

If the dynamometer speed or torque falls outside the speed or torque tolerance 

for more than 2 consecutive seconds, or for more than 5 seconds total, the mode 

Page 19 Test Procedures 
§85.2 §85.2 

timer shall reset to zero and resume timing. The minimum mode length shall be 

determined as described in §85.2(d)(iii). The maximum mode length shall be 

90 seconds elapsed time (mt=90). 

During the 10 second period used for the pass decision, the dynamometer speed 

shall not fall more than 0.5 mph (absolute drop, not cumulative). If the speed at 

the end of the 10 second period is more than 0.5 mph less than the speed at the 

start of the 10 second period, testing shall continue until the speed stabilizes 

enough to meet this criterion. 

The ten second emissions window shall be matched to the corresponding 

vehicle speed trace time window. This shall be performed by subtracting the 

nominal response time for the analyzers from the mode time to determine the 

time for the corresponding vehicle speed. 

(iii) The pass/fail analysis shall begin after an elapsed time of 25 seconds (mt=25). 

A pass/fail determination shall be made for the vehicle and the mode shall be 

terminated as follows: 

(A) The vehicle shall pass the ASM5015 mode and the mode shall be 

immediately terminated if, at any point between an elapsed time of 25 

seconds (mt=25) and 90 seconds (mt=90), the 10 second running average 

measured values for each pollutant are simultaneously less than or equal 

to the applicable test standards described in §85.1(a). 

(B) Pass/Fail determinations may be made at mt=15 seconds if a 50% safety 

margin in cutpoints is applied from mt=15 to mt=25 seconds, i.e. 

emissions for all pollutants are simultaneously 50% below the appropriate 

ASM standards. 

(C) The vehicle shall fail the ASM5015 mode and the mode shall be 

terminated if the requirements of §85.2(d)(1)(iii)(A) are not satisfied by an 

elapsed time of 90 seconds (mt=90). 

(iv) Upon termination of the ASM5015 mode, the vehicle shall immediately begin 

accelerating to the speed required for the ASM2525 mode. The dynamometer 

torque shall smoothly transition during the acceleration period and shall 

automatically reset to the load required for the ASM2525 mode as specified in 

§85.2(d)(2)(i) once the roll speed specified in §85.2(d)(2)(i) is achieved. 

(2) ASM2525 Mode. 

(i) The mode timer shall start (mt=0) when the dynamometer speed (and 

corresponding power) are maintained within 25±1.0 miles per hour for 5 

continuous seconds. The dynamometer shall apply the constant torque over the 

duration of the ASM mode. Torque shall be set to the correct torque necessary 

to generate the required horsepower at 25.0 mph. If actual torque applied 

deviates by more than 2% from the target torque for more than two consecutive 

seconds, the test mode timer shall be set to mt=0. 

Page 20 Test Procedures 
§85.2 §85.2 

(ii) The dynamometer power shall be automatically selected from an EPA-supplied 

or EPA-approved look-up table, based upon the vehicle identification 

information described in §85.2(a)(1). If a vehicle is not specifically listed in the 

EPA-approved table, default values from the same table shall be used. If an 

appropriate default value is not available in the EPA-approved table, ASM 

loading should be taken from the following table: 

Default ASM2525 Actual Horsepower Settings 

For 8.6" Dynamometers HP25258 

Vehicle Type Number of Cylinders 

3 4 5 & 6 8 > 8 

Sedans 

Station Wagons 

Mini-vans 

Pickup Trucks 

Sport/Utility 

Full Vans 

6.7 

6.8 

8.8 

8.0 

8.8 

9.0 

9.5 

9.7 

11.7 

10.9 

11.2 

11.6 

11.5 

11.5 

13.2 

13.6 

12.9 

14.7 

13.7 

13.4 

14.9 

16.0 

16.1 

16.3 

13.3 

13.3 

15.3 

17.8 

17.8 

17.2 

Default ASM2525 Actual Horsepower Settings 

For 20" Dynamometers HP252520 

Vehicle Type Number of Cylinders 

3 4 5 & 6 8 > 8 

Sedans 

Station Wagons 

Mini-vans 

Pickup Trucks 

Sport/Utility 

Full Vans 

6.9 

7.0 

8.9 

8.1 

8.9 

9.1 

10.1 

10.4 

12.5 

11.4 

11.8 

12.5 

12.3 

12.2 

14.0 

14.4 

13.6 

15.5 

14.5 

14.2 

15.9 

16.9 

17.1 

17.3 

14.3 

14.4 

16.3 

18.8 

18.8 

18.3 

If the dynamometer speed or torque falls outside the speed or torque tolerance 

for more than two consecutive seconds, or for more than 5 seconds total, the 

mode timer shall reset to zero and resume timing. The minimum mode length 

shall be determined as described in §85.2(d)(2)(iii). The maximum mode length 

shall be 90 seconds elapsed time (mt=90). 

During the 10 second period used for the pass decision, the dynamometer speed 

shall not fall more than 0.5 mph (absolute drop, not cumulative). If the speed at 

the end of the 10 second period is more than 0.5 mph less than the speed at the 

start of the 10 second period, testing shall continue until the speed stabilizes 

enough to meet this criterion. 

Page 21 Test Procedures 
§85.2 §85.2 

(iii) The pass/fail analysis shall begin after an elapsed time of 25 seconds (mt=25). 

A pass or fail determination shall be made for the vehicle and the mode shall be 

terminated as follows: 

(A) The vehicle shall pass the ASM2525 mode if, at any point between an 

elapsed time of 25 seconds (mt=25) and 90 seconds (mt=90), the 10-

second running average measured values for each pollutant are 

simultaneously less than or equal to the applicable test standards 

described in §85.1(a). If the vehicle passed the ASM5015 mode, as 

described in §85.2(d)(1)(iii), the ASM2525 mode shall be terminated 

upon obtaining passing scores for all three pollutants. If the vehicle 

failed the ASM5015 mode, the ASM2525 mode shall continue for an 

elapsed time of 90 seconds (mt=90). 

(B) Pass/Fail determinations may be made at mt=15 seconds if a 50% safety 

margin in cutpoints is applied from mt=15 to mt=25 seconds, i.e. 

emissions for all pollutants are 50% below the appropriate ASM 

standards. 

(C) The vehicle shall fail the ASM2525 mode and the mode shall be 

terminated if the requirements of §85.2(d)(2)(iii)(A) are not satisfied by 

an elapsed time of 90 seconds (mt=90). 

(3) Alternative ASM2525 (ASM5015) Test Procedure 

(i) The Alternative ASM2525 (ASM5015) test cycle consists of three modes as 

depicted qualitatively below. (The same figure may be applied to the 

Alternative ASM5015 test if one simply recognizes that the y-axis speed value 

in this case should be 15 mph rather than 25 mph.) Mode 1 is 30 seconds in 

duration at 25 mph (15 mph), Mode 2 is a short duration speed variation, and 

Mode 3 is 135 seconds at 25 mph (15 mph). 

(ii) The timers for Mode 1 and Mode 3 shall start when the vehicle speed, 

dynamometer loading and dilution are within the test limits specified above in 

§85.2(d) (specifically §85.2(d) (1)(i) and §85.2(d)(1)(ii) for the ASM5015 or 

§85.2(d) (2)(i) and §85.2(d)(2)(ii) for the ASM2525) for 2 continuous seconds 

and no low flow error is recorded. 

(iii) In Mode 1, the vehicle shall pass the test and the test shall be terminated 

immediately if at any point between 15 and 30 seconds the 10 second running 

average measured values for each pollutant are simultaneously less than or 

equal to 50% of the applicable standards. 

(iv) If the 10 second running average measured values for each pollutant are not 

simultaneously less than or equal to 50% of the applicable standards, a speed 

variation up to 30 mph in 2 seconds, down to 20 mph in 4 seconds and back to 

25 mph in 2 seconds shall be performed. During the speed variation there are 

no acceleration or speed limits; however, the target speeds must be reached. 

Page 22 Test Procedures 
§85.2 §85.2 

(v) For the ASM5015 test, the speed variation is from 15 mph to 20 mph, down to 

10 mph and back to 15 mph in the same time increments outlined above for the 

ASM2525. 

(vi) When the vehicle has returned to 25 mph (15 mph) for 2 seconds, Mode 3 shall 

begin. 

(vii) The vehicle shall pass the test and the test shall be terminated immediately if at 

any point between 15 and 30 seconds the 10 second running average measured 

values for each pollutant are simultaneously less than or equal to 50% of the 

applicable standards. 

(viii) Starting at Second 31 in Mode 3, the vehicle shall pass the test and the test shall 

be terminated immediately if the 10 second running average measured values 

for each pollutant are simultaneously less than or equal to the applicable 

standards. 

Qualitative Illustration of Alternative ASM Test Procedure 

35 

30 

25 

Mode 1 

30 sec. 

Mode 3 

135 sec. 

Mode 2 

Velocity (mph) 20 

15 

10 

5 

0 

Time (s) 

(e) Second Chance Tests. 

(1) If the vehicle fails the first-chance test, the test timer shall reset to zero and a secondchance test shall be performed, except as noted below. If the vehicle is not tested 

within 20 minutes of failing the test it shall be preconditioned by driving the vehicle at 

the designated test speed and appropriate inertia weight settings for an additional 60 

seconds prior to the start of the retest. The second-chance test shall be of the same 

maximum duration as the first chance test. As each test mode is roughly 90 seconds 

long, the total maximum test time can vary accordingly depending on whether a one or 

two mode ASM test is implemented. A retest on only one mode would increase the 

Page 23 Test Procedures 
§85.2 §85.2 

total test time to roughly 180 seconds, while performing a retest for each mode on a 

vehicle that failed both modes would extend the total test time to approximately 360 

seconds. 

Depending on the length of time it takes to perform the speed wiggle in the Alternative 

ASM Test Procedure, the maximum time for a single mode should be roughly 170-180 

seconds. Retesting a failed vehicle could double this time to 340-360 seconds. 

Therefore, although the Alternative ASM Test Procedure is designed to improve a 

vehicle’s chances of passing, performing retests using this procedure could double the 

overall test time versus the Original ASM Test Procedure. 

(2) For vehicles that fail one mode of a two mode ASM test, the failed mode may be 

repeated or extended as described below. An exception to this would be in the case of 

vehicles already subjected to preconditioning as specified in §85.2(b)(12)(i) or if at 

least 90 seconds of loaded preconditioning were performed, as specified in 

§85.2(b)(12)(ii), then the second-chance test may be omitted. 

(i) If the vehicle failed only the first mode (ASM5015) of the first chance test, then 

that mode shall be repeated upon completion of the second mode (ASM2525). 

The repeated mode shall be performed as described in §85.2(d)(1) except that 

the provisions of §85.2(d)(1)(iv) shall be omitted. The test will terminate when 

the mode ends or when the vehicle passes, whichever occurs first. 

(ii) If the vehicle is failing only the second mode (ASM2525) of the first chance 

test, then the second mode shall not end at 90 seconds but shall continue for up 

to 180 seconds. Mode and test timers shall not reset but rather continue up to 

180 seconds. The provisions of §85.2(d)(2) shall continue to apply throughout 

the 180 second test period. 

(iii) If the vehicle failed both modes (ASM5015 and ASM2525) of the first chance 

test, then the vehicle shall receive a second-chance test for the ASM5015. If the 

vehicle fails the second-chance ASM5015, then the vehicle shall fail the test. 

Otherwise, the vehicle shall also receive a second-chance ASM2525. 

Page 24 Test Procedures 
§85.3 §85.3 

§85.3 Test Equipment Specifications 

(a) Dynamometer Specifications*. 

(1) General Requirements 

(i) While dynamometer roll diameters may range from 8.5” to 21”, it is preferable 

that only one diameter of dynamometer roll be used throughout each program 

whenever possible. 

(ii) The dynamometer structure (e.g., bearings, rollers, pit plates, etc.) shall 

accommodate all light-duty vehicles and light-duty trucks up to 8500 pounds 

GVWR and axle weights up to 6,000 lbs. 

(iii) Dynamometer ASM load horsepower (HP5015 or HP2525) shall be 

automatically selected based on the vehicle parameters in the test record. 

(iv) All dynamometers shall have an identification plate permanently affixed 

showing at a minimum, the dynamometer manufacturers name, the system 

provider's name, production date, model number, serial number, dynamometer 

type, maximum axle weight, maximum HP absorbed, roll diameter, roll width, 

base inertia weight, and electrical requirements. 

(v) The dynamometer shall be designed to meet specifications at an ambient 

temperature range of 35° to 110°F, and at absolute humidity values 

representative of the testing location. A wider range of operating temperatures 

shall be used to reflect local operating conditions if applicable. 

(vi) Dynamometers shall be equipped with both torque and speed test points to be 

used during audits. Test points shall be easily accessed with test clips. The 

torque signal shall be a DC voltage free of electrical noise. Maximum absorbed 

torque shall produce between +5 and +10 volts of signal. Maximum motored 

torque shall produce between -5.0 and -10.0 volts. The speed signal shall 

consist of a 5 volt pulse signal that can be counted by an external pulse counter. 

Alternative designs will be considered on a case-by-case basis. 

(vii) Alternative dynamometer specifications, designs or error checking may be 

allowed if proposed by a state and upon a determination by the Administrator 

that, for the purpose of properly conducting an approved short test, the evidence 

supporting such deviations show that proper vehicle loading will be applied. 

*

 NOTE: Throughout the specification, whenever dynamometer inertia weight is used in an equation, the units should be 

referenced as “lbs” and coast-down times should be referenced in “seconds”. 

Page 25 7/28/04 Test Equipment Specifications 
§85.3 §85.3 

(2) Power Absorption. 

(i) Vehicle Loading. The vehicle loading used during the ASM driving cycles 

shall follow the equation in §85.3(a)(2)(ii) at 15 and 25 mph. Unless otherwise 

noted, any horsepower displayed during testing shall be expressed as HP*

. 

(ii) Indicated Horsepower. At constant velocity, the power absorber shall load the 

vehicle according the following equations: 

IHP = TRLHP - PLHP - GTRL 

Where: IHP is the dynamometer indicated, or set, horsepower. 

TRLHP is the track, or total, horsepower for a particular vehicle. 

PLHP is Parasitic Losses Horsepower due to internal 

dynamometer friction. Parasitic losses are specific to each 

dynamometer and are a function of speed. 

GTRL is Generic Tire/Roll Interface Losses at the specified 

speed. For two-wheel-drive dynamometers, values may either be 

taken directly from the EPA-approved Look-up Table, or be 

calculated according to the procedures outlined in the EPA’s 

IM240 Equipment Specification. 

TRLHP, PLHP, GTRL, and therefore IHP, are all expressed as three term 

polynomials of the type: 

HP = A*Obmph + B*Obmph2 + C*Obmph3 

Where: HP represents individual expressions relating IHP, TRLHP, 

PLHP, or GTRL as a function of velocity. 

A, B, or C represent horsepower coefficients for the individual 

expressions relating IHP, TRLHP, PLHP, or GTRL as a function 

of velocity. 

Obmph is the velocity in miles per hour. 

Expressions for TRLHP, and GTRL are found in Appendices H and I of the 

IM240 Guidance 

(iii) Range of Power Absorber. The range of the power absorber shall be sufficient 

to simulate the load required to perform an ASM5015 and an ASM2525 on all 

light-duty vehicles and light-duty trucks with ETW values up to 7,500 lbs. And 

*

 This is the actual Horsepower value contained in the look-up table for a vehicle being tested (using the ASM5015 or 2525) 

on a dynamometer with the specified diameter rollers. It is the sum of the Indicated Horsepower and the Parasitic Losses. 

Page 26 Test Equipment Specifications 
§85.3 §85.3 

5015 tire losses of 3.3 HP. To this end, the power absorber shall be sufficient to 

absorb a peak load of 33.3 hp at 14 mph for five minutes straight. In addition, 

the power absorber shall be sufficient to absorb and dissipate energy from 

continuous cycles consisting of five minutes of 25 horsepower at 14 mph 

followed by three minutes at rest. 

(iv) Power Absorber. Only electric power absorbers shall be used unless 

alternatives are proposed by the state and approved by the Administrator. The 

power absorber shall be adjustable in 0.1 hp increments at both 15 MPH and 25 

MPH. The accuracy of the power absorber (PAU + parasitic losses) shall be 

±0.25 horsepower or ±2% of required power, whichever is greater, in either 

direction of rotation. For field auditing the accuracy shall be ±0.5 horsepower. 

(v) Accuracy Over the Operating Range. The dynamometer's accuracy when warm 

shall not deviate more than ±0.5 horsepower over the full ambient operating 

range of 35°F to 110°F. This may be accomplished by intrinsic design or by 

software correction techniques. At any constant temperature, the dynamometer 

shall have an accuracy of ±0.5 horsepower within 15 seconds from the time the 

rolls start turning, and shall have an accuracy of ±0.25 horsepower within 30 

seconds from the time the rolls start turning. For temperatures outside the 

specified range, the dynamometer shall provide correction or proceed with a 

manufacturer warm-up sequence until full warm condition has been reached. 

(3) Inertia. 

(i) Test Inertia. The dynamometer shall be equipped with mechanical flywheel(s) 

or with full inertia simulation providing an inertia weight of 2000 pounds ±40 

pounds. Any deviation from the 2000 pound base inertia shall be quantified and 

the coast-down time shall be corrected accordingly. 

For all-wheel-drive dynamometers that may be operated in either two- or fourwheel-drive modes, the inertia in two-wheel-drive mode must comply with the 

above requirements. The inertia in four-wheel-drive mode may be different, 

however it shall be quantified to within 10 lbs. 

The actual test inertia weight shall be marked on the ID plate required in 

§85.3(a)(1)(iv). In the case of all-wheel-drive dynamometers, the test inertia 

must be displayed for both two- and all-wheel-drive operation. 

(ii) Inertia/Inertia Simulation. The dynamometer shall be capable of conducting, at 

a minimum, diagnostic level transient inertia simulations with an acceleration 

rate between 0 and 3.3 miles per hour per second with a minimum load (power) 

of 25 horsepower at 14 mph over the inertia weight range of 2000 pounds to 

6000 pounds. For the diagnostic level inertia simulation, the 25 horsepower 

criterion is a requirement on acceleration only, while for the full inertia 

simulation option, the requirement is for both acceleration and deceleration. 

Mechanical inertia simulation shall be provided in 500 pound increments; 

electric inertia simulation shall be provided in 1 pound increments. Any 

Page 27 Test Equipment Specifications 
§85.3 §85.3 

deviation from the stated inertia shall be quantified and the inertia simulation 

shall be corrected accordingly. Mechanical or electrical inertia simulation, or a 

combination of both, may be used, subject to review and approval by the state. 

(A) Diagnostic Level Simulation. 

1. System Response. The torque response to a step change shall be at 

least 90% of the requested change within 300 milliseconds. 

2. Simulation Error. An inertia simulation error (ISE) shall be 

continuously calculated any time the actual dynamometer speed is 

between 10 MPH and 60 MPH. The ISE shall be calculated by the 

equation in §85.3(a)(3)(ii)(C), and shall not exceed 3% of the inertia 

weight selected (IWs) for the vehicle under test. 

(B) Full Inertia Simulation. (Recommended Option) 

1. System Response. The torque response to a step change shall be at 

least 90% of the requested change within 300 milliseconds. Torque 

response shall settle to within 2% of the requested change within 600 

milliseconds. 

2. Simulation Error. Horsepower simulation error (HPSE) shall be 

continuously calculated any time the dynamometer speed is greater 

than 5 mph. The HPSE is defined as the average difference between 

the desired power (DP) and the achieved power (AP) in 10 

measurements taken at 0.5-second sequential intervals over the 

previous 5 seconds, divided by the total power (TP = inertia plus 

road load). However, if augmented braking is applied or the desired 

PAU power is less than or equal to zero*

 during any 0.5-second 

measurement, then the difference between the desired and achieved 

power for that 0.5-second measurement shall be set to 0. Values set 

to be 0 shall be used in the 5-second moving averages. If TP is less 

than 5HP over the 5-second period, set TP to 5HP. 

(C) Horsepower Simulation Error Calculation. 

i −10 

∑ (DP − 

HPSE = i 

∑

−10 

) 

i 

i 

TP 

AP

*

 This shall only apply to eddy current dynamometers, not full electric dynamometers. 

Page 28 Test Equipment Specifications 
§85.3 §85.3 

Where: 

i - current 0.5-second interval, starting at second 5 

DP -desired power (inertia plus road load minus GTRL and PLHP) 

AP - achieved power (measured at the load cell) 

TP - total power (inertia plus road load) 

A violation occurs if HPSE is greater than ±0.25%. 

(4) Parasitic Losses. 

(i) The parasitic losses (PLHP) in each dynamometer system (including but not 

limited to windage, bearing friction, and system drive friction) shall be 

characterized at 15 and 25 mph upon initial acceptance, and during each 

dynamometer calibration. The parasitic power losses shall be determined as 

indicated in §85.4(b)(2). 

(ii) For all-wheel-drive dynamometers that can be operated in either two or fourwheel-drive modes, parasitic losses must be characterized in both modes. 

Software controlling the dynamometer must automatically adjust programmed 

parasitic losses depending upon the mode in which the dynamometer is 

operating. 

(5) Rolls. 

(i) Size and Type. The dynamometer shall be equipped with twin rolls. The rolls 

shall be coupled side to side. In addition, the front and rear rolls shall be 

coupled. The dynamometer roll diameter shall be between 8.5 and 21.0 inches. 

The spacing between the roll centers shall comply with the equation in 

§85.3(a)(5)(iii). The dynamometer rolls shall accommodate an inside track 

width of 30 inches and an outside track width of at least 100 inches. 

(ii) Roll Installation. Rolls shall be installed in the floor such that vehicles will be 

be reasonably level when tested. The system shall be designed and installed 

such that ±8 degrees of level is achieved for vehicles having an 86” wheelbase 

and 27” outer diameter tires; an 89” wheelbase and 18” outer diameter tires; and 

a 170” wheelbase with 33” outer diameter tires. Either in-floor or aboveground installations are acceptable providing they meet these criteria. 

(iii) Roll Spacing. The spacing between the roll centers shall comply with the 

following equation to within +0.5 inches and -0.25 inches. 

Roll Spacing = (24.375 + D) * Sin 31.5 

Where: Roll Spacing is the distance between the roll centerlines in inches. 

D= Roll diameter in inches 

Page 29 Test Equipment Specifications 
§85.3 §85.3 

(iv) Roll Surface. The surface finish and hardness shall be such that tire slippage is 

minimized when testing vehicles using the inertia weight and horsepower 

settings found in the EPA I/M Look-up Table while following the driving 

schedule, and that tire wear and noise are minimized. Knurled roll surfaces are 

acceptable*

. 

(v) Vehicle Lift. A vehicle lift system located between the dynamometer rolls shall 

be provided to facilitate drive axle positioning and vehicle egress from the 

dynamometer. 

(vi) Vehicle Restraint System. The system shall include a system of safely 

restraining the forward and side-to-side motion of front wheel drive vehicles, 

and the forward motion of rear wheel drive vehicles during the driving 

schedule, while allowing unobstructed ingress and egress from the 

dynamometer. 

(6) Load Measuring Device 

(i) Torque Measurement. The dynamometer shall have a torque measurement 

system accurate to within ±2% of full scale. 

(ii) Dead Weights. Dead weights used to calibrate a torque meter or load measuring 

device shall be traceable to NIST and be accurate to within ±0.5%. Dead 

weights traceable to standards other than NIST may be used upon approval of 

the Administrator. 

(iii) Dynamic Calibrations. Designs using an F = MA method for calibrating the 

load cell are also acceptable; however, systems using such dynamic calibrations 

must provide an external means of accurately determining base inertia or 

performing load cell calibrations. 

(7) All-Wheel-Drive-Dynamometers. 

(i) Design. The dynamometer shall meet the requirements for two-wheel-drive 

vehicles and be capable of testing traction control and all-wheel-drive vehicles 

in a safe manner without damaging the vehicle. 

(ii) Wheelbase. The all-wheel-drive dynamometer shall be capable of testing 

vehicles having wheelbases ranging from 84 to 125 inches. The separation 

between the front and rear dynamometer rolls shall be automatically adjustable 

in increments of 1.00” or less and shall be accurate to ±0.25” of the selected 

vehicle wheelbase. Once a vehicle is positioned on the dynamometer, the 

* It should be noted that knurlling or altering the surface of the dynamometer will effect the GTRL coefficients. However, at 

this time it is believed that the impact such alterations may have will be minimal and not affect emissions measurements. 

Page 30 Test Equipment Specifications 
§85.3 §85.3 

dynamometer must allow the vehicle to be centered on the dynamometer, 

including fine tuning the roll separation as necessary to meet the actual 

wheelbase of the vehicle within 0.1”. After the roll separation matches the 

vehicle, the dynamometer must automatically lock the roll separation prior to 

the beginning of loaded testing. The roll separation lock must be sufficient to 

maintain the roll separation to within 0.25” of the vehicle wheelbase when 1000 

lbs of force is applied to either compress or extend the dynamometer roll 

separation. 

(iii) Speed Synchronization. Front and rear rolls shall maintain speed 

synchronization within ±0.1 mph during steady-state operation. During 

transient speed operation, secondary roll speed must be maintained within ±0.1 

mph or 1% of the primary roll speed, whichever is greater. Since many traction 

control vehicles will not be equipped with all-wheel drive, the secondary rolls 

must have sufficient power to drive and maintain speed for the non-drive 

wheels without assistance from the vehicle. 

(iv) Bi-directionality. Dynamometers in which one set of rolls is considered 

primary (i.e., drive wheels for non-all-wheel-drive vehicles must be place on 

one set) must be bi-directional. This will allow both front- and rear-wheel-drive 

vehicles to be tested in all-wheel-drive mode. 

(v) Disengageable Secondary Rolls. Dynamometers may be configured so that 

secondary rolls may be automatically disengaged when all-wheel-drive testing 

is not required. If the secondary rolls are disengaged, the system shall 

automatically compensate for the change in parasitic losses and base inertia as 

well and the change in generic tire roll losses. 

(vi) Base inertia. All-wheel-drive dynamometers that can be operated in either twoor all-wheel-drive modes must account for changes in base inertia resulting 

from the two different configurations. 

(8) Other Requirements. 

(i) Vehicle Speed. The measurement of roll speed shall be accurate within 0.1 mph 

over the full operating range. The dynamometer shall accommodate vehicle 

speeds of up to 60 mph. 

(ii) Vehicle Restraint. In §85.2(b)(10). 

(iii) Vehicle Cooling. In §85.2(c)(6). 

(iv) Four-Wheel Drive. If used, four-wheel drive dynamometers shall insure the 

application of correct vehicle loading as defined in §85.3(a)(2), shall not 

damage the four wheel drive system of the vehicle, and shall accommodate 

vehicles equipped with anti-lock brakes and/or traction control. Front and rear 

wheel rolls shall maintain speed synchronization within 0.2 mph. 

(v) Installation. In §85.3(a)(5)(ii). 

Page 31 Test Equipment Specifications 
§85.3 §85.3 

(vi) Augmented Braking. Dynamometers shall apply augmented braking on major 

decelerations during transient drive cycles, if such cycles are used in the 

program. The dynamometer software shall provide a signal output to inform the 

operator when augmented braking is activated. Augmented braking shall be 

actuated only when the negative force applied by the vehicle at the roll surface 

is greater than 110 lbs. Augmented braking shall be applied so that at least 50% 

of the braking force beyond 110 lbs required to meet the deceleration 

requirements of the drive trace is absorbed by the dynamometer. 

(b) Emission Sampling System. 

(1) The sampling system shall be designed to insure durable, leak free operation and be 

easily maintained. Materials that are in contact with the gases sampled shall not 

contaminate or change the character of the gases to be analyzed, including gases from 

vehicles not fueled by gasoline (except diesels). The system shall be designed to be 

corrosion-resistant and be able to withstand typical vehicle exhaust temperatures when 

the vehicle is driven through the ASM test cycle for the maximum test length described 

in §85.2(e). 

(2) The sampling system shall draw exhaust gas from the vehicle, shall remove particulate 

matter and aerosols from the sampled gas, shall drain condensed water from the sample 

if necessary, and shall deliver the resultant gas sample to the analyzers/sensors for 

analysis and then deliver the analyzed sample directly outside the building. The 

sampling system shall, at a minimum, consist of a tailpipe probe, flexible sample line, 

water removal system, a particulate trap, sample pump, and flow control components. 

(3) Sample Probe. 

(i) Insertion. The sample probe shall allow at least a 16 inch insertion depth of the 

sample probe into the vehicle's exhaust. In addition, the probe shall be inserted 

at least 10 inches into the vehicle's exhaust. Use of a tailpipe extension is 

permitted as long as the extension does not change the exhaust back pressure by 

more than ±1.0 inch of water pressure. 

(ii) Retention. The probe shall incorporate a positive means of retention to 

prevent it from slipping out of the tailpipe during use. High through-put test 

systems may use alternative means to insure probe retention. 

(iii) Flexibility. The probe shall be designed so that the tip extends 16 inches into 

the tailpipe. The probe tip shall be shielded so that debris is not scooped up by 

the probe when it is inserted into the tailpipe. High through-put test systems 

may use alternative means to insure adequate probe insertion. 

(iv) Probe Tip. Probe tips shall be designed and constructed to prevent sample 

dilution. 

(v) Materials. All materials in contact with exhaust gas prior to and throughout the 

measurement portion of the system shall be unaffected by and shall not affect 

Page 32 Test Equipment Specifications 
§85.3 §85.3 

the sample (i.e., the materials shall not react with the sample, and they shall not 

taint the sample). Acceptable materials include stainless steel, Teflon, silicon 

rubber, and Tedlar. Dissimilar metals with thermal expansion factors of more 

than 5% shall not be used in either the construction of probes or connectors. 

The sample probe shall be constructed of stainless steel or other non-corrosive, 

non-reactive material which can withstand exhaust gas temperatures at the 

probe tip of up to 1,100o

F for 10 minutes. 

(vi) System Hoses and Connections. Hoses and all other sample handling 

components must be constructed of, or plated with a non-reactive, noncorrosive, high temperature material which will not affect, or be affected by, the 

exhaust constituents and tracer gases. 

(vii) Dual Exhaust. The sample system shall provide for the testing of dual exhaust 

equipped vehicles. When testing a vehicle with functional dual exhaust pipes, a 

dual sample probe of a design certified by the analyzer manufacturer to provide 

equal flow in each leg shall be used. The equal flow requirement is considered 

to be met if the flow rate in each leg of the probe has been measured under two 

sample pump flow rates (the normal rate and a rate equal to the onset of low 

flow), and if the flow rates in each of the legs are found to be equal to each 

other (within 15% of the flow rate in the leg having lower flow). 

(4) Particulate Filter. The particulate filter shall be capable of trapping 97% of all 

particulate and aerosols 5 microns or larger. The filter element shall not absorb or 

adsorb hydrocarbons. The filter housing shall be transparent or translucent to allow the 

operator to observe the filter element’s condition without removing the housing. The 

filter element shall be easily replaceable and shall provide for reliable sealing after 

filter element changes. 

(5) Water Trap. The water trap shall be sized to remove exhaust sample water from 

vehicles fueled with gasoline, propane, compressed natural gas, reformulated gasoline, 

alcohol blends or neat, and oxygenated fuels. The filter element, bowl and housing 

shall be inert to these fuels as well as to the exhaust gases from vehicles burning these 

fuels. The condensed water shall be drained from the water trap’s bowl either 

continuously or automatically on a periodic basis such that the following performance 

requirement is maintained. Sufficient water shall be trapped, regardless of fuel, to 

prevent condensation in the sample system or in the optical bench’s sample cell. 

(6) Low Flow Indication. The analyzer shall lock out official testing when the sample flow 

is below the acceptable level. The sampling system shall be equipped with a flow 

meter (or equivalent) that shall indicate sample flow degradation when measurement 

error exceeds 3% of the gas value used for checking, or causes the system response 

time to exceed 13 seconds to 90 percent of a step change in input (excluding NO), 

whichever is less. Alternatively, the sample vacuum may be continuously monitored to 

detect a low flow condition. 

(7) Exhaust Ventilation System. The high quantities of vehicle emissions generated during 

loaded mode testing shall be properly vented to prevent buildup of hazardous 

concentrations of HC, CO, CO2 and NOx. Sufficient ventilation shall be provided in 

Page 33 Test Equipment Specifications 
§85.3 §85.3 

the station to maintain HC, CO, CO2 and NO levels below recommended Occupational 

Safety and Health Association (OSHA) standards*

. 

(i) The ventilation system shall discharge the vehicle exhaust outside the building. 

(ii) The flow of the exhaust collection system shall not cause dilution of the exhaust 

at the sample point in the probe. 

(iii) The flow of the exhaust collection system shall not cause a change of more than 

±1.0 inches of water pressure in the vehicle's exhaust system at the exhaust 

system outlet. 

(c) Analytical Instruments. 

(1) General Requirements. 

(i) Measured Gases. The analyzer system shall consist of analyzers for HC, CO, 

NO, and CO2, (O2 optional). It is recommended that the system provide digital 

displays for exhaust concentrations of HC, CO, NO, and CO2, as well as for 

vehicle speed; however, it is recognized that some BAR97 systems do not 

provide these features. 

(ii) Emission Accuracy. The system shall ensure that the analytical system provides 

an accurate accounting of the actual exhaust emissions produced during the test, 

taking into consideration the individual channel accuracy, repeatability, 

interference effects, sample transport times, and analyzer response times. 

(iii) Sample Rate. The analyzer shall be capable of measuring exhaust 

concentrations of the gases specified in §85.3(c)(1)(i) at a minimum rate of once 

per second. 

(iv) Alternative Equipment. Alternative analytic equipment specification, materials, 

designs, or detection methods may be allowed if proposed by a state and upon a 

determination by the Administrator, that for the purpose of properly conducting 

a test, the evidence supporting such deviations will not significantly affect the 

proper measurement of emissions. 

(2) Performance Requirements. 

(i) Temperature Operating Range. The analyzer system and all associated 

hardware shall operate within the performance specifications described in 

§85.3(c)(3) at ambient air temperatures ranging from 35oF to 110oF. Analyzers 

shall be designed so that adequate air flow is provided around critical 

components to prevent overheating (and automatic shutdown) and to prevent the 

condensation of water vapor which could reduce the reliability and durability of 

* The following limits may be found in 29 CFR 1910.1000 Table Z-1. CO 50 ppm; CO2 5000 ppm; NO2 5 ppm; n-Hexane 

500 ppm; Propane 1000 ppm. 

Page 34 Test Equipment Specifications 
§85.3 §85.3 

the analyzer. The analyzer system shall otherwise include necessary features to 

keep the sampling system within the specified range. 

(ii) Humidity Operating Range. The analyzer system and all associated hardware 

shall operate within the performance specifications described in §85.3(c)(3) at a 

minimum of 85% relative humidity throughout the required temperature range. 

(iii) Interference Effects. The interference effects for non-interest gases shall not 

exceed ±4 ppm for hydrocarbons, ±0.02% for carbon monoxide, ±0.20% for 

carbon dioxide, and ±20 ppm for nitric oxide when using the procedure 

specified in §85.4(d)(5)(iv). Corrections for collision-broadening effects of 

combined high CO and CO2 concentrations shall be taken into account in 

developing the factory calibration curves, and are included in the accuracy 

specifications. 

(iv) Barometric Pressure Compensation. Barometric pressure compensation shall be 

provided. Compensation shall be made for elevations up to 6000 feet (above 

mean sea level). At any given altitude and ambient conditions specified in 

§85.3(c)(2)(i) and (ii), errors due to barometric pressure changes of ±2 inches of 

mercury shall not exceed the accuracy limits specified in §85.3(c)(3). 

(iv) System Lockout During Warm-up. Functional operation of the gas sampling 

unit shall remain disabled through a system lockout until the instrument meets 

stability and warm-up requirements. The instrument shall be considered 

"warm" when the zero and span readings for HC, CO, NO, and CO2 have 

stabilized, within the accuracy values specified in §85.3(c)(3) for five minutes 

without adjustment. 

(v) Zero Drift Lockout. If zero or span drift cause the optical bench signal levels to 

move beyond the adjustment range of the analyzer, the system shall be locked 

out from testing. 

(vi) Electromagnetic Isolation and Interference. Electromagnetic signals found in 

an automotive service environment shall not cause malfunctions or changes in 

the accuracy in the electronics of the analyzer system. The instrument design 

shall ensure that readings do not vary as a result of electromagnetic radiation 

and induction devices normally found in the automotive service environment, 

including high energy vehicle ignition systems, radio frequency transmission 

radiation sources, and building electrical systems. 

(vii) Vibration and Shock Protection. System operation shall be unaffected by the 

vibration and shock encountered under the normal operating conditions 

encountered in an automotive service environment. 

(viii) Propane Equivalency Factor. The nominal PEF range shall be between 0.490 

and 0.540. For each audit/calibration point, the nominal PEF shall be 

conveniently displayed for the quality assurance inspector and other authorized 

personnel. Ideally, the PEF shall appear on the monitor in conjunction with the 

HC reading during any audit or at the operator’s request. 

Page 35 Test Equipment Specifications 
§85.3 §85.3 

If an optical bench must be replaced in the field, any external labels shall be 

changed to correspond to the nominal PEF of the new bench. The analyzer 

shall incorporate an algorithm relating PEF to HC concentration. Corrections 

shall be made automatically. The corrected PEF value may cover the range of 

0.470 to 0.560 

(ix) System Response Requirements. The response time from the probe to the 

display for HC, CO, and CO2 analyzers shall not exceed 8 seconds for 90% of a 

step change in input, nor shall it exceed 12 seconds to 95% of a step change in 

input. The response time for a step change in O2 from 20.9% O2 to 0.1% O2 

shall be no longer than 40 seconds. For NO analyzers, the response time shall 

not exceed 12 seconds for 90% of a step change in input. The response time for 

a step change in NO from a stabilized reading to 10% of that reading shall be no 

longer than 12 seconds. 

(3) Detection Methods, Instrument Ranges, Accuracy, and Repeatability. 

(i) Hydrocarbon Analysis. Hydrocarbon analysis shall be determined by nondispersive infrared (NDIR) analyzer. The analyzer shall cover at least the range 

of 0 ppm HC to 9999 ppm HC, where ppm HC is parts per million of 

hydrocarbon volume as hexane. The accuracy of the instrument from 0-2000 

ppm HC shall be ±3% of point or 4 ppm C6, whichever is greater. The 

accuracy of the instrument between 2001 ppm HC and 5000 ppm HC shall be at 

least ±5% of point and the accuracy of the instrument between 5001 ppm HC 

and 9999 ppm HC shall be at least ±10% of point. The instrument shall comply 

with the quality control specifications in §85.4(d). 

(ii) Carbon Monoxide Analysis. Carbon monoxide analysis shall be determined by 

non-dispersive infrared (NDIR) analyzer. The analyzer shall cover at least the 

range of 0.00 % CO to 14.00% CO, where % CO is % volume CO. The 

accuracy of the instrument between 0.01% and 10.00% CO shall be ±3% of 

point or 0.02% CO, whichever is greater. The accuracy of the instrument 

between 10.01% and 14.00% shall be at least ±5% of point. The instrument 

shall comply with the quality control specifications in §85.4(d). 

(iii) Carbon Dioxide Analysis. Carbon dioxide analysis shall be determined by nondispersive infrared (NDIR) analyzer. The analyzer shall cover at least the range 

of 0.0 % CO2 to 18.0% CO2. The accuracy of the instrument between 0.01% 

and 16.00% CO2 shall be ±3% of point or 0.3% CO2, whichever is greater. The 

accuracy of the instrument between 16.01% and 18.00% shall be at least ±5% of 

point. The instrument shall comply with the quality control specifications in 

§85.4(d). 

(iv) Nitric Oxide Analysis. The analyzer shall cover at least the range of 0 ppm NO 

to 5000 ppm NO, where ppm NO is parts per million nitric oxide. The accuracy 

of the instrument between 0 and 4000 ppm shall be at least ±4% of point or 25 

ppm NO, whichever is greater. The accuracy of the instrument between 4001 

and 5000 ppm shall be at least ±8% of point. The instrument shall comply with 

the quality control specifications in §85.4(d). 

Page 36 Test Equipment Specifications 
§85.3 §85.3 

(v) Oxygen Analysis. (optional) If an oxygen analyzer is included, the analyzer 

shall cover at least the range of 0.0% O2 to 25.0% O2. The accuracy of the 

instrument over this range shall be at least 5% of point or ±0.1% O2, whichever 

is greater. The instrument shall comply with the quality control specifications 

in §85.4(d). 

(vi) Repeatability. The repeatability for the HC analyzer in the range of 0-1400 ppm 

HC shall be 2% of point or 3 ppm HC absolute, whichever is greater. In the 

range of 1400-2000 ppm HC, the repeatability shall be 3% of point. The 

repeatability for the CO analyzer in the range of 0-7.00% CO shall be 2% of 

point or 0.02% CO absolute, whichever is greater. In the range of 7.00% to 

10.00% CO, the repeatability shall be 3% of point. The repeatability for the 

CO2 analyzer in the range of 0-10.0% CO2 shall be 2% of point or 0.1% CO2 

absolute, whichever is greater. In the range of 10.0% to 16.0% CO2, the 

repeatability shall be 3% of point. The repeatability of the NO analyzer shall be 

3% of point or 20 ppm NO, whichever is greater. The repeatability of the O2 

analyzer shall be 3% of point or 0.1% O2, whichever is greater. 

(vii) Rounding Rule. Rounding beyond the decimal places shown in §85.3(c)(3) 

shall follow the standard mathematical practice of going to the next higher 

number for any numerical value of five or more. This shall also hold true for 

pass/fail decisions. For example, if 2.00% CO passes and 2.01% CO fails, and 

the reading is 2.0049%, the value shall be rounded down and the decision shall 

be a pass. If the reading is 2.0050, the value shall be rounded up and the 

decision shall be a fail. The value displayed and printed on the test report shall 

be consistent with the value used for the pass/fail decision. 

(4) Ambient Conditions. The current relative humidity, dry-bulb temperature, and 

barometric pressure shall be measured and recorded prior to the start of every 

inspection in order to calculate Kh (nitric oxide correction factor §85.1(b)(1)(vi)). 

(i) Relative Humidity. The relative humidity measurement device shall cover the 

range from 5% to 95% RH, between 35o

F - 110oF, with a minimum accuracy of 

±3% RH. Wet bulb thermometers shall not be used. 

(ii) Dry-bulb Temperature. The dry-bulb temperature device shall cover the range 

from 0o

F - 140oF with a minimum accuracy of 3oF. 

(iii) Barometric Pressure. The barometric pressure measurement device shall cover 

the range from 610 mm Hg - 810 mm Hg absolute (24-32 inches), and 35o

F -

110o

F, with a minimum accuracy of ±3% of point or better. 

(5) Engine Speed Detection. The analyzer shall utilize a tachometer capable of detecting 

engine speed in revolutions per minute (RPM) with a 0.5 second response time and an 

accuracy of ±3% of the true RPM. On vehicles equipped with onboard diagnostic 

(OBD) systems, it is recommended that the engine speed be taken by connecting to the 

SAE standardized OBD link on 1996 and newer vehicles. RPM readings shall be 

recorded on a second-by-second basis for the 10 second period upon which the pass/fail 

decision is based. 

Page 37 Test Equipment Specifications 
§85.3 §85.3 

(6) OBD Fault Code Retrieval. Starting in 2001 the system shall include the hardware and 

software necessary to access the onboard computer systems on 1996 and newer 

vehicles, determine OBD readiness, and recover stored fault codes using the SAE 

standardized link. 

(d) Automated Test Process Software and Displays. 

(1) Software. The testing process, data collection, and quality control features of the 

analyzer system shall be automated to the greatest degree possible. The software shall 

automatically select the emission standards and set the vehicle load based on an EPAprovided or approved look-up table. Vehicle identification information shall be derived 

from a database accessed over a real-time data system to a host computer system. 

Entry of license plate and all or part of the VIN shall be sufficient to access the vehicle 

record. Provision shall be made for manual entry of data for vehicles not in the host 

computer system. Alternative methods for matching test records to the appropriate 

vehicle and ensuring that the vehicle is tested using the proper parameters may be used 

if approved by the Administrator. 

(2) Test and mode timers. The analyzer shall be capable of simultaneously determining the 

amount of time elapsed in a test (overall test time), and in a mode within that test (mode 

time). 

(3) Clocks and Timers. The clock used to check the coast-down time shall be accurate to 

within 0.1% of reading between 0.5 and 100 seconds, with a resolution of 0.001 

seconds. The test mode timers used shall be accurate to within 0.1% of reading 

between 10 and 1000 seconds with a resolution of 0.1 seconds. 

(4) Driver's Aid. The system shall be equipped with a driver's aid that shall be clearly 

visible to the driver as the test is performed. The aid shall continuously display the 

required speed, the number of seconds into the test mode, the driver's actual speed/time 

performance (a display showing the deviation between set-point and actual driving 

trace), engine RPM, the use of augmented braking, and necessary prompts and alerts. It 

is recommended that an analog speed display be used as this has been demonstrated to 

improve a driver's ability to maintain the ±1.0 mph tolerance. The driver's aid shall 

also be capable of displaying test and equipment status and other messages as required. 

Dynamic information being displayed shall be refreshed at a minimum rate of twice per 

second. Emissions values shall not be displayed during official testing. 

(5) Minimum Analyzer Display Resolution. The analyzer electronics shall have sufficient 

resolution to achieve the following: 

HC 1 

NO 1 

CO 0.01 

CO2 0.1 

O2 0.1 

RPM 10 

Speed 0.1 

ppm HC as hexane

ppm NO

% CO

% CO2

% O2 (optional)

RPM

mph

Page 38 Test Equipment Specifications 
§85.3 §85.3 

Load 0.1 hp 

Relative Humidity 1 % RH 

Dry Bulb Temperature 1 oF 

Barometric Pressure 1 mm Hg 

Page 39 Test Equipment Specifications 
§85.4 §85.4 

§85.4 Quality Control Requirements 

(a) General Requirements 

(1) Minimums. The frequency and standards for quality control specified here are 

minimum requirements, unless modified as specified in §85.4(a)(2). Greater frequency 

or tighter standards may be used as needed. 

(2) Statistical Process Control. Reducing the frequency of the quality control checks, 

modifying the procedure or specification, or eliminating the quality control checks 

altogether may be allowed if the state demonstrates and the Administrator determines, 

for the purpose of properly conducting an approved short test, that sufficient Statistical 

Process Control (SPC) data exist to make a determination, that the SPC data support 

such action, and that taking such action will not significantly reduce the quality of the 

emissions measurements. Should emission measurement performance or quality 

deteriorate as a result of allowing such actions, the approval shall be suspended and the 

frequencies, procedures specifications, or checks specified here or otherwise approved 

shall be reinstated, pending further determination by the Administrator. 

(b) Dynamometer 

(1) Coast Down Check. 

(i) The calibration of each dynamometer shall be automatically checked every 72 

hours in low volume stations (less than 4000 tests per year) and daily in high 

volume stations by a dynamometer coast-down procedure equivalent to 40 CFR 

§86.118-78 (for reference see National Vehicle and Fuel Emission Laboratory's 

Testing Services Division test procedure TP-302A and TP-202) between the 

speeds of 30-20 mph if the ASM2525 is used and 20-10 mph if the ASM5015 is 

used. All rotating dynamometer components shall be included in the coastdown check. Speed windows smaller than ± 5 mph may be used provided that 

they show the same calibration capabilities. 

(ii) The dynamometer calibration shall be checked at two random horsepower 

settings for each speed range using the 2000 lb. test inertia. The two random 

horsepower settings shall be between 8.0 and 18.0 horsepower. The random 

selection shall be evenly distributed throughout the 8 to 18 HP range. A shunt 

resistor for a load cell performance check shall not be used. 

(iii) The coast-down procedure shall use a vehicle-off-dynamometer type method or 

equivalent. Using a vehicle to bring the dynamometer up to speed and 

removing the vehicle before the coast-down shall not be permitted. If either the 

measured 30-20 mph coast-down time or 20-10 mph coast-down time is outside 

the window bounded by the Calculated Coast-Down Time (CCDT) (seconds) ± 

6% then it shall be locked out for official testing purposes until recalibration 

allows a passing value. 

Page 40 7/28/04 Quality Control Requirements 
§85.4 §85.4 

If the dynamometer fails a coast-down check, a parasitic loss determination 

shall be required and performed automatically. 

(A) Randomly select an IHP2525 value that is between 8.0 hp and 18.0 hp and 

set dynamometer PAU to this value. 

Coast-down dynamometer from 30-20 mph. 

0.5*DIW 2 2 

32.2 

*(V30 − V20 ) 

CCDT@25mph = 

550*(IHP2525 + PLHP25 ) 

Where: 

DIW = Dynamometer Inertia Weight. Total "inertia" weight 

of all rotating components in dynamometer. 

V30 = Velocity in feet/sec at 30 mph. 

V20 = Velocity in feet/sec at 20 mph. 

IHP2525 = Randomly selected ASM2525 indicated horsepower. 

PLHP25 = Parasitic Horsepower for specific dynamometer at 25 

mph. 

(B) Randomly select an IHP5015 value that is between 8.0 hp and 18.0 hp and 

set dynamometer PAU to this value. 

Coast-down dynamometer from 20-10 mph. 

0.5*DIW 2 2 

32.2 

* (V20 − V10 ) 

CCDT@15mph = 

550 * (IHP5015 + PLHP15 ) 

Where: 

DIW = Dynamometer Inertia Weight. Total "inertia" weight 

of all rotating components in dynamometer. 

V20 = Velocity in feet/sec at 20 mph. 

V10 = Velocity in feet/sec at 10 mph. 

IHP5015 = Randomly selected ASM5015 indicated horsepower. 

PLHP15 = Parasitic Horsepower for specific dynamometer at 15 

mph. 

Page 41 Quality Control Requirements 
§85.4 §85.4 

(2) Parasitic Value Calculations. Parasitic losses should be measured any time service is 

performed on a dynamometer, as the first step in diagnosing a dynamometer’s inability 

to pass a coast-down, or if the load measuring device is re-calibrated. 

(i) Parasitic losses shall be calculated using the following equations at 25 and 15 

mph whenever a coast-down check is performed, except the indicated 

horsepower (IHP) shall be set to zero for these tests. Parasitic losses shall be 

determined using the equations listed below. After new parasitic values are 

calculated, the coast-down check procedure contained in §85.4(b)(1) must be 

passed before the dynamometer can be returned to service. 

(ii) Parasitic losses at 25 mph for a dynamometer with specified diameter rollers. 

0.5*DIW 2 2 

32.2 

* (V30 − V20 ) 

PLHP25 = 

550 * (ACDT) 

Where: 

DIW = Dynamometer Inertia Weight. Total "inertia" weight 

of all rotating components in dynamometer. 

V30 = Velocity in feet/sec at 30 mph. 

V20 = Velocity in feet/sec at 20 mph. 

ACDT = Actual coast-down time required for dynamometer to 

coast from 30 to 20 mph. 

(iii) Parasitic losses at 15 mph for a dynamometer with specified diameter rollers. 

0.5*DIW 2 2 *(V20 − V10 )

PLHP15 = 

32.2 

550*(ACDT) 

Where: 

DIW = Dynamometer Inertia Weight. Total "inertia" weight 

of all rotating components in dynamometer. 

V20 = Velocity in feet/sec at 20 mph. 

V10 = Velocity in feet/sec at 10 mph. 

ACDT = Actual coast-down time required for dynamometer to 

coast from 20 to 10 mph. 

Page 42 Quality Control Requirements 
§85.4 §85.4 

(3) Roll Speed. There is no need to perform roll speed checks on a regular basis, providing 

the coast-down procedures are being performed and adhered to. This is because 

dynamometers will not be able to pass the coast-down test with erroneous speed 

readings, especially when the load is changed from coast-down to coast-down. 

(4) Load Measuring Device. If the dynamometer fails a coast-down check immediately 

after performing a parasitic loss determination, then the dynamometer load measuring 

device may be malfunctioning or out of calibration. In this case, or in the case of the 

load measuring system being serviced, the load-measuring device shall be checked 

using a dead-weight method or an equivalent procedure proposed by the state and 

approved by the Administrator. The check shall cover at least three points over the 

range of loads used for vehicle testing. Dead weights shall be traceable to the National 

Institute of Standards (NIST) and shall be accurate to within ±0.1%. Dead weights 

traceable to standards other than NIST may be used upon approval of the 

Administrator. The dynamometer shall provide an automatic load measuring device 

calibration and verification feature. 

(5) Certification Testing. 

(i) Load Cell Verification (if equipped). This test confirms the proper operation of 

the dynamometer load cell and associated systems. Weights in the proper range 

shall be supplied by the system supplier. Weights shall be NIST traceable to 

0.1% of point. Dead weights traceable to standards other than NIST may be 

used upon approval of the Administrator. 

(A) Calibrate the load cell according to the manufacturer's direction. 

(B) Using a dead weight method, load the test cell to 20%, 40%, 60%, and 

80% (in ascending order) of the range used for ASM testing. Record the 

readings for each weight. Remove the weights in the same steps 

(descending order) and record the results. 

(C) Perform steps A through B two more times (total of three). Calculate the 

average value for each weight. Multiply each average weight from E by 

the length of the torque arm. 

(D) Acceptance Criteria: The difference for each reading from the weight 

shall not exceed 1% of full scale. 

(ii) Speedometer Verification. This test confirms the accuracy of the 

dynamometer's speedometer. 

(A) Measure the dynamometer roll diameter to within ±0.01 inch. This may 

be accomplished using a PI tape. If the dynamometer is able to motor to a 

constant speed, set the dynamometer speed to 15 mph. If the dynamometer 

does not have the ability to motor at constant speeds, place a vehicle on 

the dynamometer and drive the vehicle at a constant speed as close to 15 

mph as possible. Independently measure and record dynamometer roll 

rotational frequency using a frequency counting device such as a strobe 

tachometer. Mathematically convert the roll diameter to circumference 

Page 43 Quality Control Requirements 
§85.4 §85.4 

and multiply by the rotational frequency to obtain linear speed. Compare 

this speed to the speed measured by the test system. Repeat at 25 mph. 

(B) Acceptance Criteria: The difference for each reading from set 

dynamometer speed shall not exceed 0.1 mph. 

(iii) Parasitics Verification. Parasitic losses shall be verified at 25 and 15 mph using 

the procedure in §85.4(b)(2), using time data from a system independent source 

(e.g. stopwatch) and speed data from the system. The indicated horsepower 

(IHP) shall be set to zero for these tests. 

(A) Acceptance Criteria: The difference between the externally calculated 

value and the machine calculated value shall not exceed 10% of the 

independently measured value. 

(iv) Verify Coast-Down. The coast-down procedure shall use a vehicle offdynamometer type method or equivalent. Using a vehicle to bring the 

dynamometer up to speed and removing the vehicle before the coast-down shall 

not be permitted. 

(A) To verify the coast-downs at 25 mph, use the procedure and equations 

described in §85.4(b)(2)(ii). 

(B) To verify the coast-downs at 15 mph, use the procedure and equations 

described in §85.4(b)(2)(iii). 

(C) Acceptance Criteria: The measured 30-20 mph coast-down time and the 

20-10 mph coast-down time must be inside the window bounded by 

CCDT (seconds) ± 6% at both speeds. 

(6) Field Auditing. 

(i) Frequency. Field audits should be performed on each dynamometer at least 

once per year (A) Calibrate the load cell according to the manufacturer's 

direction. 

(ii) Perform coast-down check to verify system does not self diagnose any 

problems. Correct any problems as necessary. 

(iii) Dynamometer load verification may be performed either with an existing 

dynamometer tester or by reading voltage directly from the dynamometer load 

cell. If an existing dynamometer tester is used, follow the directions provided 

by the tester manufacturer. If voltage measurement is used, follow the 

directions below: 

(A) Determine the ratio for converting load cell voltage into dynamometer 

load. 

(B) Test a known vehicle on the ASM test while measuring voltage at the 

load cell. 

Page 44 Quality Control Requirements 
§85.4 §85.4 

(C) Determine vehicle load by plugging known values into the loading 

equation found in §85.3.a.2.ii. Determine vehicle load by plugging 

known values into the loading equation found in §85.3.a.2.ii. 

(D) Compare the applied load with the target load from the EPA-approved 

lookup table (or the applicable table for the particular emissions 

inspection program) 

(c) Emission Sampling System. 

(1) Leak Check. The entire sample system shall be checked for vacuum leaks on a daily 

basis and proper flow on a continuous basis. This may be accomplished using a 

vacuum decay method, reading a span gas, or other methods proposed by a state and 

approved by the Administrator. The analyzer shall not allow an error of more than 1% 

of reading using the high-range span gas described in §85.4(d)(2)(iii)(C). The analyzer 

shall be locked out from testing if the leak check is not performed when due or fails to 

pass the check. 

(2) Dilution. The flow rate on the analyzer shall not cause more than 10% dilution during 

sampling of exhaust of a 1.6 liter engine a normal idle. Ten percent dilution is defined 

as a sample of 90% exhaust and 10% ambient air. 

(3) Dilution Acceptance Test. 

(i) Set vehicle with 1.6 liter maximum engine displacement at factory -

recommended idle speed, OEM configuration exhaust system, transmission in 

neutral, hood up (a fan to cool the engine may be used if needed). Set idle 

speed not to exceed 920 RPM. (Set for 900 RPM with a tolerance ± 20 RPM.) 

(ii) With a laboratory grade analyzer system, sample the exhaust at 40 centimeters 

depth with a flow sample rate below 320 liters per hour. Allow sufficient time 

for this test. Record all HC, CO, NO, CO2, and O2 readings. A chart recorder or 

electronically stored data may be used to detect the point of stable readings. 

(iii) While operating the candidate analyzer system in a mode which has the same 

flow rate as the official test mode, record the levels of HC, CO, NO, CO2, and 

O2. Ensure that the probe is installed correctly. 

(iv) Repeat step (ii). 

(iv) Acceptance Criteria: If the difference of the readings between (ii) and (iv) 

exceed five percent of the average of (ii) and (iv), repeat (ii), (iii), and (iv); 

otherwise average (ii) and (iv) and compare with (iii). If (iii) is within 10 

percent of the average of (ii) and (iv), then the equipment meets the dilution 

specification. 

Page 45 Quality Control Requirements 
§85.4 §85.4 

(d) Analytic Instruments. 

(1) General Requirements. The analyzer shall, to the extent possible, maintain accuracy 

between gas calibrations taking into account all errors, including noise, repeatability, 

drift, linearity, temperature, and barometric pressure. 

(2) Two-Point Gas Calibration and Low-Range Audit. 

(i) Analyzers shall automatically require a zero gas calibration and a high-range 

gas calibration for HC, CO, NO, and CO2. The system shall also use a lowrange gas to check the calibration in the range of vehicle emission standards. In 

high volume stations (4000 or more tests per year), analyzers shall be calibrated 

within four hours before each test. In low volume stations (below 4000 tests per 

year), analyzers shall be calibrated within 72 hours before each test. If the 

system does not calibrate or is not calibrated, the analyzer shall lock out from 

testing until corrective action is taken. This calibration check shall include 

measuring the NO cell response to ensure it is < 15 seconds with a warning 

displayed when the response exceeds 7 seconds. 

(ii) Gas Calibration and Check Procedure. Gas calibration shall be accomplished 

by introducing calibration gases that meet the requirements of §85.4(d)(2)(iii) 

into the calibration port. The pressure in the sample cell shall be the same with 

the calibration gas flowing as with the sample flowing during testing. The 

analyzer channels shall be adjusted to the center of the allowable tolerance 

range as a result of the calibration. The system shall record the gas reading data 

from before the adjustment and other data pertinent to control charting analyzer 

performance. 

(A) Zero the analyzer and perform a leak check. 

(B) Calibrate the analyzer using the low and high-range calibration gas as 

specified in §85.4(d)(2)(iii). 

(C) Purge the analyzers completely by flowing the low-range calibration gas 

specified in §85.4(d)(2)(iii) for 60 seconds. If the low-range calibration 

gas readings differ from the true cylinder value by more ±3% of point for 

HC, ±3% of point for CO, ±3% of point for CO2, or ±25 ppm NO the 

analyzer shall be locked out from testing. 

(iii) The following gases shall be used for the 2-point calibration and low-range 

audit. The Low- and High-Range Calibration Gases are the same concentrations 

and purity as the Low- and High-Range Audit Gases. 

Appendix A contains a table with sample calculations illustrating how the Low 

and High Audit Limits for the Calibration Gases are to be determined. The 

tolerances are based on a 2% blend tolerance, accurate to 1%. It is 

Page 46 Quality Control Requirements 
§85.4 §85.4 

recommended that NIST traceable standards accurate to 1% be used to verify all * bottle names . 

(A) Zero Gas 

O2 = 20.7% 

HC < 1 ppm THC 

CO < 1 ppm 

CO2 < 400 ppm 

NO < 1 ppm 

N2 = Balance 99.99 % pure 

(B) Low-Range Calibration Gas 

HC = 200 ppm propane 

CO = 0.5 % 

CO2 = 6.0 % 

NO = 300 ppm 

N2 = Balance 99.99 % pure 

(C) High-Range Calibration Gas 

HC = 3200 ppm propane 

CO = 8.0 % 

CO2 = 12.0 % 

NO = 3000 ppm 

N2 = Balance 99.99 % pure 

(iv) Traceability. The audit and span gases used for the gas calibration shall be 

traceable to National Institute of Standards and Technology (NIST) standards 

±1%. Gases shall have a 2% blend tolerance. 

(3) Five-Point Calibration Audit. 

(i) Analyzers shall automatically require and successfully pass a five point gas 

audit for HC, CO, NO, and CO2. For high volume stations, audits shall be 

checked monthly. In low volume stations, analyzers shall undergo the audit 

procedure every six months. 

(ii) Gas Audit Procedure. Calibration auditing shall be accomplished by 

introducing audit gas through the probe. The pressure in the sample cell shall 

be the same with the audit gas flowing as with the sample flowing during 

testing. 

(A) Zero the analyzer and perform a leak check. 

* EPA has been informed that adherence to this minimum NIST standard may not be an ironclad guarantee of accuracy. 

Requiring gases to be analyzed using EPA-600/R-97-121 may be a more reliable method; however, it may also cause a 

significant increase in cost. 

Page 47 Quality Control Requirements 
§85.4 §85.4 

(B) Flow the low range audit gas specified in §85.4(d)(3)(iii) through the 

sample probe, ensuring that the tip is equal to ambient barometric pressure 

±0.1 inches Hg (a balloon teed into the gas flow line is an acceptable 

pressure indicator; the balloon should stand slightly erect). 

(C) When the HC, CO, NO, and CO2 gases have been flowing for 60 seconds 

record the readings as well as the PEF value for HC at each audit blend. 

(D) Repeat steps B and C for each audit gas specified in §85.4(d)(3)(iii). 

(E) Compare the readings with the audit gas values using the equation listed 

below. Be sure to divide the HC reading by its PEF if this calculation is 

not performed automatically in the analyzer software. 

Tolerance % = 100 * (Reading − True Cylinder Value) 

True Cylinder Value 

(F) If the analyzer response when reading any of the Audit Gases exceeds 

±4.0% for HC/PEF, CO, and CO2, or ±5.0% for NO, then the analyzer 

shall fail the gas audit and shall be locked out from testing until it passes. 

(iv) The following gases shall be used for the five-point calibration audit. 

(A) Zero Audit Gas 

O2 = 20.7% (if O2 span is desired) 

HC < 0.1 ppm THC 

CO < 0.5 ppm 

CO2 < 1 ppm 

NO < 0.1 ppm 

N2 = Balance 99.99 % pure 

(B) Low Range Audit Gas 

HC = 200 ppm propane 

CO = 0.5 % 

CO2 = 6.0 % 

NO = 300 ppm 

N2 = Balance 99.99 % pure 

(C) Low-Middle Range Audit Gas 

HC = 960 ppm propane 

CO = 2.4 % 

CO2 = 3.6 % 

NO = 900 ppm 

N2 = Balance 99.99 % pure 

(D) High-Middle Range Audit Gas 

HC = 1920 ppm propane 

CO = 4.8 % 

CO2 = 7.2 % 

NO = 1800 ppm 

Page 48 Quality Control Requirements 
§85.4 §85.4 

N2 = Balance 99.99 % pure 

(E) High Range Audit Gas 

HC = 3200 ppm propane 

CO = 8.0 % 

CO2 = 12.0 % 

NO = 3000 ppm 

N2 = Balance 99.99 % pure 

(iv) Traceability. These gases shall be traceable to National Institute of Standards 

and Technology (NIST) standards ±1%. Gases shall have a 2% blend tolerance. 

(4) Service, Repair and Modification. 

(i) Each time an analyzer's emissions measurement system, sensor, or other related 

electronic components are repaired or replaced, the five point calibration audit 

required in §85.4(d)(3) shall be performed, at a minimum, prior to returning the 

unit to service. 

(ii) Each time the sample line integrity is broken, a leak check shall be performed 

prior to testing. 

(5) Certification Testing. 

(i) Analyzer accuracy. This test confirms the ability of the candidate instruments 

to read various concentrations of gases within the tolerances required by this 

specification. The test compares the response of the candidate instrument with 

that of standard instruments, and also estimates the uncertainty of the readings. 

The analyzer shall be zeroed and gas calibrated using the high-range calibration 

gas. The instrument shall be tested using propane, carbon monoxide, carbon 

dioxide, and nitric oxide in nitrogen, with a certified accuracy of ±1%, in the 

following concentrations: 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 

90%, and 100% of the high range audit gas 

(A) Introduce the gases in ascending order of concentrations beginning with 

the zero gas. Record the readings of the standard and candidate 

instruments to each concentration value. A gas divider may be used to 

divide the high range audit gas to the concentrations described in 

§85.4(d)(5)(i). 

(B) After the highest concentration has been introduced and recorded, 

introduce the same gases to the standard and candidate analyzers in 

descending order, including the zero gas. Record the reading of analyzers 

to each gas, including negatives (if any). 

(C) Repeat steps A and B for the candidate only, four more times (total of five 

times). 

(D) Calculation Procedure: 

Page 49 Quality Control Requirements 
§85.4 §85.4 

1. Calculate the average value of each concentration for the readings 

of the standard instruments. 

2. Calculate the mean and standard deviation of each candidate's 

readings for each concentration. Include both upscale and 

downscale readings for the same gas concentration. (All 

calculations may not be possible for zero concentrations.) 

3. For each concentration, calculate the difference between the 

candidate mean and the standard average. 

4. For each concentration, compute the following: 

(i) Y1 = x + Ksd 

(ii) Y2 = x - Ksd 

Where 

Ksd = std dev * 3.5 for zero and the highest concentration value

Ksd = std dev * 2.5 for all other concentration values

x = mean (arithmetic average) of the set of candidate readings.

5. Compute the uncertainty (U) of the calibration curve for each 

concentration as follows: 

(i) U1 = concentration value - Y1 

(ii) U2 = concentration value - Y2 

6. Acceptance Criteria: 

(a) For each concentration, the differences calculated in Step 3 

shall be no greater than the accuracy tolerances specified in 

§85.3(c)(3) for each instrument. 

(b) For each concentration, the uncertainties, (U1 and U2) shall 

be no greater than the accuracy tolerances required in 

§85.3(c)(3). 

(E) Alternative Calculation Procedure: 

1. Use a gas divider readings as the standard values and compare 

them to the measured values of a sample lot of instruments 

2. Compute the absolute and percent of point deltas using the 

equation in Section §85.4(d)(3)(ii)(E). 

3. For each point, the instruments shall pass the criteria provided in 

Section §85.4(d)(3)(ii)(F). 

(ii) Analyzer System Repeatability. This test characterizes the ability of the 

instrument to give consistent readings when repeatedly sampling the same gas 

concentration. 

Page 50 Quality Control Requirements 
§85.4 §85.4 

(A) Using the high range span gas, introduce the gas through the calibration 

port. Record the readings. 

(B) Purge with ambient air for at least 30 seconds but no more than 60 

seconds. 

(C) Repeat steps A and B above four more times. 

(D) Repeat steps A, B, and C, introducing the gas through the sample probe. 

(E) Acceptance Criteria: The differences between the highest and lowest 

readings from both ports shall not exceed the values specified in 

§85.3(c)(3)(vi). 

(iii) Analyzer System Response Time. This test determines the speed of response of 

the candidate instrument when a sample is introduced at the sample probe. 

(A) Gas calibrate the candidate instrument per the manufacturer's instructions. 

(B) Using a solenoid valve or equivalent selector system, remotely introduce 

an high range span gas to the probe. The gas pressure at the entrance to 

the probe shall be equal to room ambient. 

(C) Measure the elapsed time required for the instrument display to read 90% 

and 95% of the final stabilized reading for HC, CO, CO2 and NO. 

(Optional: Also, measure the time required for the O2 analyzer to read 

0.1% O2). Alternatively the bench outputs may be recorded against a time 

base to determine the response time. Record all times in seconds. 

(D) Switch the solenoid valve to purge with zero air for at least 40 seconds but 

no more than 60 seconds. 

(E) Measure the elapsed time required for the NO instrument display to read 

10% of the stabilized reading in Step C. 

(F) Repeat steps A, B, and C, two more times (total three times). 

(G) Acceptance Criteria: The response (drop time for O2 and NO; rise time for 

HC, CO, CO2 and NO) times shall meet the requirement specified in 

§85.3(c)(2)(x). The response time shall also be within ±1 second of the 

nominal response time supplied by the equipment supplier for use in 

§85.5(b)(5). 

(iv) Analyzer Interference Effects. The following acceptance test procedure shall be 

performed at 45o

F, 75oF, and 105oF conditions, except as noted. 

(A) Zero and span the instrument. 

(B) Sample the following gases for at least one minute. Record the response 

of each channel to the presence of these gases. 

Page 51 Quality Control Requirements 
§85.4 §85.4 

1. 16% Carbon Dioxide in Nitrogen. 

2. 1600 ppm Hexane in Nitrogen. 

3. 10% Carbon Monoxide in Nitrogen. 

4. 3000 ppm Nitric Oxide in Nitrogen. 

5. 75 ppm Sulfur Dioxide (SO2) in Nitrogen. 

6. 75 ppm Hydrogen Sulfide (H2S) in Nitrogen. 

(C) Water-Saturated Hot Air. Water-saturated hot air shall be drawn through 

the probe from the top of a sealed vessel partially filled with water 

through which ambient air will be bubbled. The water shall be 

maintained at a temperature of 122o

F ± 9oF. This test shall be performed 

at only the 75oF, and 105oF conditions. 

(D) Acceptance Criteria: The interference effects shall not exceed the limits 

specified in §85.3(c)(2)(iii). 

(v) Electromagnetic Isolation and Interference. This test shall measure the ability 

of the candidate instrument to withstand electromagnetic fields which could 

exist in vehicle testing and repair facilities. For all tests described below, 

sample "Low-Middle Range Audit Gas" specified in §85.4(d)(3)(iii)(C), at 

atmospheric pressure, through the sample probe. Record analyzer reading 

during test periods. 

(A) Radio Frequency Interference Test. 

1. Use a test vehicle with an engine having a high energy ignition 

system (or equivalent), a solid core coil wire and a 3/8" air gap. 

Leave engine off. 

2. Locate the candidate instrument within 5 feet of the ignition coil. 

Gas calibrate the candidate instrument. 

3. Sample gas specified above. Wait 20 seconds, and record analyzer 

readings. 

4. Start engine. With the hood open and gas flowing to the analyzer, 

cycle the engine from idle through 25 mph on the dynamometer at 

ASM loads and record the analyzer readings. 

5. Relocate the instrument to within 6 inches of one side of the 

vehicle near the engine compartment. Follow procedure described 

in step 4 and record analyzer readings. 

6. Relocate the instrument to within 6 inches of the other side of the 

vehicle near the engine compartment. Follow procedure described 

in step 4 and record analyzer readings. 

7. Acceptance Criteria: The analyzer readings shall deviate no more 

than 0.5% full scale. 

Page 52 Quality Control Requirements 
§85.4 §85.4 

(B) Induction Field Test. Use a variable speed (commutator type) hand drill 

having a plastic housing and rated at 3 amps or more. While the analyzer 

is sampling the gas, vary the drill speed from zero to maximum while 

moving from the front to the sides of the instrument at various heights. 

Acceptance Criteria: The analyzer readings shall deviate no more than 

0.5% full scale. 

(C) Line Interference Test. Plug the drill used in part B above into one outlet 

of a #16-3 wire extension cord approximately 20 feet long. Connect the 

instrument into the other outlet of the extension cord. Repeat part B 

above. 

Acceptance Criteria: The analyzer readings shall deviate no more than 

0.5% full scale. 

(D) VHF Band Frequency Interference Test. Locate both a citizens ban radio 

(CB), with output equivalent to FCC legal maximum, and a highway 

patrol transmitter (or equivalent) within 50 feet of the instrument. While 

the analyzer is sampling the gas, press and release transmit button of the 

both radios several times. 

Acceptance Criteria: The analyzer readings shall deviate no more than 

0.5% full scale. 

(E) Ambient Conditions Instruments. Upon installation and every six months 

thereafter, the performance of the ambient conditions instruments shall be 

cross-checked against a master weather station. 

Acceptance Criteria: The individual instruments shall be within the 

tolerance specified in §85.3(c)(4). 

(v) Ambient Conditions Instruments. Upon installation and every six months 

thereafter, the performance of the ambient conditions instruments shall be cross 

checked against a master weather station. 

Acceptance Criteria: The individual instruments shall be within the tolerance 

specified in §85.3(c)(4). 

Page 53 Quality Control Requirements 
§85.5 §85.5 

§85.5 Test Record Information 

The following information shall be collected for each test performed (both passing and failing 

tests), recorded in electronic form, and made available to EPA upon request. 

(a) General Information. 

(1) Test Record Number

(2) Inspection station and inspector numbers

(3) Test system number

(4) Dynamometer site

(5) Date of test

(6) Emission test start time and the time final emission scores are determined.

(7) Vehicle identification number

(8) License plate number

(9) Test certificate number

(10) Vehicle model year, make, and type

(11) Number of cylinders or engine displacement

(12) Transmission type

(13) Odometer reading

(14) Type of test performed (i.e., initial test, first retest, or subsequent retest)

(b) Ambient Test Conditions. 

(1) Relative humidity (%)

(2) Dry-bulb temperature (o

F).

(3) Atmospheric pressure (mm Hg)

(4) NO correction factor

(5) Nominal response time for each instrument (Transport + T90)

(c) ASM Mode or Modes. 

The following information shall be captured separately for each test mode (ASM5015 and/or

ASM2525) performed.

(1) Final HC running average (AvgHC) (ppm)

(2) Final CO running average (AvgCO) (%)

(3) Final NO running average (AvgNO) (ppm)

(4) Total horsepower used to set the dynamometer (THP5015) (hp)

(5) Engine RPM running average corresponding to the final test score

(6) Dilution correction factor (DCF)

(d) Diagnostic/Quality Assurance Information. 

(1) Test time (seconds)

(2) Mode time (seconds)

(3) Vehicle speed (mph) for each second of the test

(4) Engine RPM for each second of the test

(5) Dynamometer load (pounds) for each second of the test

(6) HC concentration (ppm) for each second of the test, not corrected for dilution

(7) CO concentration (%) for each second of the test, not corrected for dilution

Page 54 7/28/04 Test Record Information 
§85.5 §85.5 

(8) NO concentration (ppm) corrected for humidity for each second of the test, not 

corrected for dilution 

(9) CO2 concentration (%) for each second of the test 

(10) O2 concentration (%) for each second of the test (optional) 

Page 55 Test Record Information 
§85.5 §85.5 

Appendix A: Calculating Audit Tolerances 

“Actual Cylinder” field is input by the auditor in ppm or %. Audit limits are calculated and filled in by 

the spreadsheet (or the auditor). The tolerances are based on a 2% blend tolerance, accurate to 1%. It is 

recommended that NIST traceable standards accurate to 1% be used to verify all bottle names. 

Spreadsheet for Calculating ASM Audit Tolerances 

Range Gas 

Gas Concentration Accuracy Audit Tolerance Applied 

Tolerance 

(greater of 

% or point) 

Audit Limits 

Recommended Actual 

Cylinder 

% of 

Reading 

Point Gas 

% of 

Reading 

% 

(as point) Point Low High 

High 

HC (ppm) 3200 3191 3.0% 8 1.0% 4.0% 128 40 128 3063 3319 

CO (%) 8.00 8.11 3.0% 0.02 1.0% 4.0% 0.32 0.10 0.32 7.79 8.43 

CO2 (%) 12.00 11.90 3.0% 0.30 1.0% 4.0% 0.48 0.42 0.48 11.42 12.38 

NO (ppm) 3000 2987 4.0% 25 1.0% 5.0% 149 55 149 2838 3136 

Mid 

High 

HC (ppm) 1920 1918 3.0% 8 1.0% 4.0% 77 27 77 1841 1995 

CO (%) 4.80 4.83 3.0% 0.02 1.0% 4.0% 0.19 0.07 0.19 4.64 5.02 

CO2 (%) 7.20 7.15 3.0% 0.30 1.0% 4.0% 0.29 0.37 0.37 6.78 7.52 

NO (ppm) 1800 1801 4.0% 25 1.0% 5.0% 90 43 90 1711 1891 

Mid 

Low 

HC (ppm) 960 960 3.0% 8 1.0% 4.0% 38 18 38 922 998 

CO (%) 2.40 2.39 3.0% 0.02 1.0% 4.0% 0.10 0.04 0.10 2.29 2.49 

CO2 (%) 3.60 3.57 3.0% 0.30 1.0% 4.0% 0.14 0.34 0.34 3.23 3.91 

NO (ppm) 900 902 4.0% 25 1.0% 5.0% 45 34 45 857 947 

Low 

HC (ppm) 200 203 3.0% 8 1.0% 4.0% 8 10 10 193 213 

CO (%) 0.50 0.49 3.0% 0.02 1.0% 4.0% 0.02 0.02 0.02 0.47 0.51 

CO2 (%) 6.00 6.01 3.0% 0.30 1.0% 4.0% 0.24 0.36 0.36 5.65 6.37 

NO (ppm) 300 299 4.0% 25 1.0% 5.0% 15 28 28 271 327 

Zero 

HC (ppm) 0 0 3.0% 8 1.0% 4.0% 0 9 9 -9 9 

CO (%) 0.00 0.00 3.0% 0.02 1.0% 4.0% 0.00 0.02 0.02 -0.02 0.02 

CO2 (%) 0.00 0.00 3.0% 0.30 1.0% 4.0% 0.00 0.30 0.30 -0.30 0.30 

NO (ppm) 0 0 4.0% 25 1.0% 5.0% 0 26 26 -26 26 

In the "Actual Cylinder" column, enter the gas concentrations from the audit cylinders 

The audit low and high tolerances are calculated in the columns on the right 

Page 56 Test Record Information