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AIR POLLUTION &

EVAPORATIVE EMISSIONS

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Hydrocarbons

Unburned fuel vapors

When exposed to sunlight, chemical

reaction occurs that producesground-level ozone O3.

Harmful to all living things

Vehicle emissions create 50% of thisozone

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Carbon Monoxide

Colorless, odorless, toxic gas

Product of incomplete combustion

Displaces oxygen which reducesoxygen in bloodstream

Vehicles produce 2/3s of co in

atmosphere

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Carbon Dioxide

Product of proper combustion

Does not directly impair human

health Greenhouse gas

Traps heat

Helping to increase global warming

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Just What is Ozone?

Ozone is a form of oxygen with adifferent chemical property

Ozone differs from oxygen: Has a distinctive odor Contains 3 oxygen atoms

Absorbs damaging ultraviolet (UV)

radiation

In large concentrations ozone ishazardous

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Earths Atmosphere

Troposphere start on the

surface and extends 59

miles

Air most dense

All weather occurs is

this region

Stratosphereextends for31 miles

Contains the Ozone layer

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Good Ozone

Blocks or absorbs most of the

suns ultraviolet rays

Approx. 3,000 million tons of

ozone in atmosphere

If concentrated at sea level,

would measure only 3 mm thick

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Bad Ozone (Smog)

Brown haze seen on hot summer days Result from burning fossil fuelschemical

reaction from heat & sun light

Health problems

Aggravates heart, lung ailments Can lower immune system

Eye & nose irritations

Environmental problems Inhibits plant growth, weakens plants

Reduce yields

Deteriorates man-made materials

Acid rain

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Evaporative EmissionsHydrocarbons escaping through fuel evaporation.

Diurnalgas evaporation as daytime

temps increase

Running Lossvaporization fromhot engine & exhaust parts

Hot Soakhot engines (off),

vaporization can continue RefuelingVapors forced out of tank

as liquid fuel enters

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Evap. Emission Control

Systems Sealed fuel tankdomed to allow for vaporexpansion

Liquid-vapor separatorwhen tank is full

fuel can enter vent lines Vent linesroutes vapor to canister &

engine

Activated charcoal canisterabsorbs fuelvapors, releases vapors with fresh air

Non venting gas cappressure/vacuumrelief valve

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Carbon Canister

Holds vapors when engine not running Engine fully warm & off idle, canister

is purged allowing fresh air in, fuel

vapors routed to engine & burned

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Canister Operation

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Purge Valve

Normally closed

Vacuum or electric solenoid

Engine off or idling valve is closed Engine running valve opens allowing

purge of canister

Solenoids either on/off or PWM

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Basic Purge Operation

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Thermostatic Vacuum

Switch (TVS)

Installed in intake manifold coolantpassage

Valve opens @ 115 F, allows vacuum to

flow

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Canister Venting

Open bottomWhen purging fresh

air enters from bottom of canister

Closed bottomfresh air enters forclean side of air filter

Electric vent solenoidPCM

controlled, allows fresh air in whencommanded, seals system when

closed.