Black smoke from car

Why is the Particulate Filter Required by Law?

13 July 2015, 13:57

When Diesel is burned in a combustion engine, much more soot is generated than by petrol-fuelled vehicles. Catalytic converters are fitted to all cars in order to make the gases which are generated in the combustion of fuel safer and more environmentally friendly, but these converters do nothing to stop particles of soot from being released into the atmosphere. This is why Diesel Particulate Filters have been introduced and made a legal requirement, to tackle the high levels of soot generated by diesel engines.

The changes to European emissions regulations, which were announced in September 2009, brought in measures to control the amount of soot which cars could legally release into the atmosphere. In order to comply with the new strict standards, all diesel vehicles manufactured after this time had to include a Diesel Particulate Filter in order to catch and trap the soot before it could be released through the exhaust.

Some of the earlier filters, which were fitted in a rush to meet the new standards, can seem to be more trouble than they are worth. They are not necessarily built using substances which can withstand the high heat which is needed to burn off the soot particles effectively and have been known to melt in some cases. Repairs and replacements can be expensive and it can seem tempting to just take out the DPF altogether, since the car will perform just as well, if not better, without it. But however tempting this may seem, it is now completely illegal.

All diesel engines in the UK are now required by law to have a Diesel Particulate Filter installed to reduce harmful soot emissions. As of February 2014, checking that a diesel car has a Diesel Particulate Filter is an official part of the MoT and diesel-powered cars will not be deemed roadworthy unless they have one fitted. This was announced by Robert Goodwill, who was the Roads Minister at the time, in a speech made in October 2013.

Since the regulations have come in so recently, car manufacturers have had relatively little time to design DPFs which function perfectly and which last for the whole lifetime of the car. If you use your vehicle to make long motorway journeys on a regular basis, then you are unlikely to have many problems with your DPF. If you drive in the city centre and rarely make journeys which are long or fast then you should consider purchasing a petrol car which does not have a DPF to avoid these problems.

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