Environmental Engineering Reference
In-Depth Information
TABLE 8.6
U.S. Vehicle Exhaust Emission Standards
Tier 1
a
NMHC
b
CO
NO
x
PM
Vehicle Type
(g/mile)
(g/mile)
(g/mile)
(g/mile)
LDV
0.25
3.4
0.4
0.08
LDT1
0.25
3.4
0.4
0.08
LDT2
0.32
4.4
0.7
0.08
LDT3
0.32
4.4
0.7
LDT4
0.39
5.0
1.1
Tier 2
c
NMOG
d
HCHO
e
CO
NO
x
PM
Vehicle Type
(g/mile)
(g/mile)
(g/mile)
(g/mile)
(g/mile)
All
0.09
4.2
0.07
0.01
0.018
Bin 7
0.125
4.2
0.20
0.02
0.018
Bin 6
0.090
4.2
0.15
0.02
0.018
Bin 5
0.090
4.2
0.07
0.01
0.018
Bin 4
0.055
2.1
0.07
0.01
0.011
Bin 3
0.070
2.1
0.04
0.01
0.011
Bin 2
0.010
2.1
0.02
0.01
0.004
Bin 1
0.000
0.00
0.00
0.00
0.000
a
Model years 1996-2007. Five years, 50,000 miles.
b
Nonmethane hydrocarbons.
c
Model years 2004-2010, except 2008-2010 for LDT3 and LDT4. Full useful life (120,000 miles).
d
Nonmethane organic gases.
e
Formaldehyde.
also not be exceeded. This new method of limiting emissions will allow manufacturers to achieve
the necessary overall reduction in their fleet's emissions as economically as possible by providing
incentives to reduce emissions below the standard in light, low-powered vehicles that may then be
credited to heavy, high-powered ones.
The Tier 2 standards, which begin with the 2004 model year, are quite stringent compared with
those of the early 1970s, when standards were first applied (see Table 9.2). For the ozone precursor
pollutants, NO
x
and NMOG, Tier 2 levels are about 2% of those for 1971 model year vehicles
and are approximately 0.2% of unregulated 1960's vehicles. This considerable reduction will be
required to make it possible to achieve ambient ozone standards in U.S. metropolitan areas in the
early part of the twenty-first century, despite increasing vehicle population and increased annual
travel per vehicle.
8.7.2
Reducing Vehicle Emissions
Vehicle exhaust pollutants are the remnants of an incomplete and nonequilibrium combustion
process in the engine cylinder. Of the mixture of fuel and air introduced into the cylinder, all
