A smog check is a test done on the exhaust system of a motor vehicle to
determine how many pollutants, and of which type, the vehicle is
emitting. The smog check also includes an assessment of other parts of
the vehicle to make sure that they are in working order, especially
those parts which pertain to emissions control. In the United States,
most states have smog check requirements which vary from state to state
in a nationwide effort to address clean air issues.
Some
states have a biannual smog check program, while others require testing
every year. Most states exempt certain vehicles from the smog check,
such as vehicles more than thirty or less than five years old. Most
states require a successful smog check to sell a vehicle, and will
require a smog certificate before the title can be transferred.
Consumers should check with their state's Department of Motor Vehicles
to find out more about the smog requirements for their area.
All states have emissions limits which vehicles cannot exceed. During a
smog check, a device is connected to the tailpipe while the engine is
run to determine the emissions of the car in idle and while being
revved, which are measured against the state standard for that type of
vehicle. The smog technician also checks to make sure that the muffler
is in working order, and usually opens the hood to make sure that all
hoses and pipes are properly connected, and that the car's internal
computer is working properly.
Emissions
loads which exceed the state limit, an improperly maintained muffler
and exhaust system, or the presence of a “check engine” light can cause
a vehicle to fail the smog check. In this instance, the vehicle must be
repaired and tested again. Most repairs to pass a smog test are
relatively simple and do not involve great expense. They are well worth
it to ensure that the vehicle is safe and legal. In some cases, the
repair may represent a substantial expense. Some states have smog
abatement programs, in which drivers who can prove that the car
requires repairs over a certain dollar amount can be exempted from smog
requirements.
Drivers should get a smog check for their vehicles regularly, not only
because it is legally required in most areas, but because if their
vehicle is not in alignment with emissions standards, it should be
repaired. Personal vehicles contribute almost 40% of pollution in some
states, and responsible drivers should aid the national effort to
reduce emissions. In addition, some factors which may cause a vehicle
to fail a smog check are also unsafe, and should be addressed to
prevent accident or injury.
At DMV.ORG, you'll find everything you need to clear the air on this sometimes confusing issue.
