Editing Diesel fuel (section)

== Hazards ==
{{See also|diesel exhaust}}

=== Environment hazards of sulfur ===

In the past, diesel fuel contained higher quantities of [[sulfur]]. [[European emission standards]] and preferential taxation have forced [[oil refinery|oil refineries]] to dramatically reduce the level of sulfur in diesel fuels. In the European Union, the sulfur content has dramatically reduced during the last 20 years. Automotive diesel fuel is covered in the European Union by standard [[EN 590]]. In the 1990s specifications allowed a content of 2000 ppm max of sulfur, reduced to a limit of 350 ppm by the beginning of the 21st century with the introduction of Euro 3 specifications. The limit was lowered with the introduction of Euro 4 by 2006 to 50 ppm ([[ULSD]], Ultra Low Sulfur Diesel). The standard for diesel fuel in force in Europe as of 2009 is the Euro 5, with a maximum content of 10 ppm.<ref>{{cite web|url=https://www.transportpolicy.net/standard/eu-fuels-diesel-and-gasoline/|title= EU: Fuels: Diesel and Gasoline|website=TransportPolicy.net|access-date=17 July 2020}}</ref>

{| class="wikitable"
! Emission standard
! At latest
! Sulfur content
! Cetane number
|-
| N/a
|align=right| 1 January 1994
|align=right| max. 2000 ppm
|align=right| min. 49
|-
| Euro 2
|align=right| 1 January 1996
|align=right| max. 500 ppm
|align=right| min. 49
|-
| Euro 3
|align=right| 1 January 2001
|align=right| max. 350 ppm
|align=right| min. 51
|-
| Euro 4
|align=right| 1 January 2006
|align=right| max. 50 ppm
|align=right| min. 51
|-
| Euro 5
|align=right| 1 January 2009
|align=right| max. 10 ppm
|align=right| min. 51
|-
|}

In the United States, more stringent emission standards have been adopted with the transition to  [[Ultra-low-sulfur diesel|ULSD]] starting in 2006, and becoming mandatory on June 1, 2010 (see also [[diesel exhaust]]).

=== Algae, microbes, and water contamination ===
{{main|microbial contamination of diesel fuel}}
There has been much discussion and misunderstanding of [[algae]] in diesel fuel. Algae need light to live and grow. As there is no sunlight in a closed fuel tank, no algae can survive, but some [[microbes]] can survive and feed on the diesel fuel.<ref>{{cite web|url=http://criticalfueltech.com/faq.html|title=What is Diesel Fuel "ALGAE"?|author=<!--Staff writer(s); no by-line.-->|year=2012|website=criticalfueltech.com|publisher=Critical Fuel Technology, Inc.|access-date=9 October 2014}}</ref>

These microbes form a colony that lives at the interface of fuel and water. They grow quite fast in warmer temperatures. They can even grow in cold weather when fuel tank heaters are installed. Parts of the colony can break off and clog the fuel lines and fuel filters.<ref>{{cite tech report|title=Microbial Contamination of Diesel Fuel: Impact, Causes and Prevention|number=253-01246|institution=Dow Chemical Company|year=2003}}</ref>

Water in fuel can damage a fuel [[injection pump]]. Some diesel [[fuel filter]]s also trap water. Water contamination in diesel fuel can lead to freezing while in the fuel tank. The freezing water that saturates the fuel will sometimes clog the fuel injector pump.<ref>{{cite web|url=http://www.afssociety.org/automotive/93-water-contamination-in-fuel-cause-and-effect|title=Water Contamination in Fuel: Cause and Effect - American Filtration and Separations Society|author=AFS admin|url-status=dead|archive-url=https://web.archive.org/web/20150323111230/http://www.afssociety.org/automotive/93-water-contamination-in-fuel-cause-and-effect|archive-date=2015-03-23}}</ref> Once the water inside the fuel tank has started to freeze, gelling is more likely to occur. When the fuel is gelled it is not effective until the temperature is raised and the fuel returns to a liquid state.

=== Road hazard ===
Diesel is less flammable than [[Gasoline|gasoline / petrol]]. However, because it evaporates slowly, any spills on a roadway can pose a slip hazard to vehicles.<ref>{{cite web|title=Oil on the road as a cause of accidents|url=http://www.icbcclaiminfo.com/node/23|publisher=ICBCclaiminfo.com|url-status=dead|archive-url=https://web.archive.org/web/20130407043946/http://www.icbcclaiminfo.com/node/23|archive-date=7 April 2013}}</ref> After the light fractions have evaporated, a greasy slick is left on the road which reduces [[tire]] grip and traction, and can cause vehicles to skid. The loss of traction is similar to that encountered on [[black ice]], resulting in especially dangerous situations for two-wheeled vehicles, such as [[motorcycle]]s and [[bicycle]]s, in [[roundabout]]s.