Passenger cars & light-duty commercial vehicles European
emissions regulations for light-duty vehicles up to 3.5 tonnes
and carrying up to 9 people including the driver - in other
words cars, 'people carriers', 4 x 4s and light vans - first
reached a level that forced the use of catalysts for petrol
engines in 1993. At that time it was still possible to use
oxidation catalysts for some vehicles, but the increasingly
stringent stages of emissions regulation since then (Euro 2 in
1997, Euro 3 in 2001, Euro 4 in 2006, Euro 5 in 2009 and Euro 6
in 2014) have ensured that three-way catalysts are universally
used for petrol engines in Europe. Typical modern systems for
vehicles with petrol or gas engines will include one or more
'close-coupled' catalysts near to the exhaust manifold and often
an additional catalyst further down the exhaust, under the floor
of the car. The exhaust system will include an oxygen sensor or
air:fuel ratio sensor that monitors the oxygen content of the
exhaust and continuously adjusts th