Editing Propane (section)

==Purity==
The North American standard grade of automotive-use propane is rated HD-5 (Heavy Duty 5%). HD-5 grade has a maximum of 5 percent butane, but propane sold in Europe has a maximum allowable amount of butane of 30 percent, meaning it is not the same fuel as HD-5. The LPG used as auto fuel and cooking gas in Asia and Australia also has very high butane content.

[[Propylene]] (also called propene) can be a contaminant of commercial propane. Propane containing too much propene is not suited for most vehicle fuels. HD-5 is a specification that establishes a maximum concentration of 5% propene in propane. Propane and other LP gas specifications are established in ASTM D-1835.<ref>{{cite web|url=http://www.astm.org/Standards/D1835.htm|title=ASTM D1835 - 16 Standard Specification for Liquefied Petroleum (LP) Gases|website=www.astm.org}}</ref> All propane fuels include an [[Aroma compound|odorant]], almost always [[ethanethiol]], so that the gas can be smelled easily in case of a leak. Propane as HD-5 was originally intended for use as vehicle fuel. HD-5 is currently being used in all propane applications.

Typically in the United States and Canada, [[Liquefied petroleum gas|LPG]] is primarily propane (at least 90%), while the rest is mostly [[ethane]], [[propylene]], [[butane]], and odorants including [[ethyl mercaptan]].<ref>{{cite web |title=Amerigas Material Safety Data Sheet for Odorized Propane |url=http://www.amerigas.com/pdfs/safe_eng.pdf |author=Amerigas |access-date=2011-10-24 |url-status=dead |archive-url=https://web.archive.org/web/20111209131917/http://amerigas.com/pdfs/safe_eng.pdf |archive-date=2011-12-09 }}</ref><ref>{{cite web |title=Suburban Propane Material Safety Data Sheet for Commercial Odorized Propane |url=http://www.suburbanpropane.com/safety/pdf/propane/SAF%205152%20MATERIAL%20SAFETY%20DATA%20SHEET.pdf |author=Suburban Propane |access-date=2011-10-24 |url-status=dead |archive-url=https://web.archive.org/web/20111025035650/http://suburbanpropane.com/safety/pdf/propane/SAF%205152%20MATERIAL%20SAFETY%20DATA%20SHEET.pdf |archive-date=2011-10-25 }}</ref> This is the HD-5 standard, (maximum allowable propylene content, and no more than 5% butanes and ethane) defined by the American Society for Testing and Materials by its Standard 1835 for internal combustion engines. Not all products labeled "LPG" conform to this standard, however. In Mexico, for example, gas labeled "LPG" may consist of 60% propane and 40% butane. "The exact proportion of this combination varies by country, depending on international prices, on the availability of components and, especially, on the climatic conditions that favor LPG with higher butane content in warmer regions and propane in cold areas".<ref>{{cite web|last=Mexican Ministry of Energy|title=Liquefied Petroleum Gas Market Outlook 2008–2017|url=http://www.energia.gob.mx/res/PE_y_DT/pub/LPG%20Outlook%202008-2017.pdf|publisher=Mexican Ministry of Energy|access-date=2012-05-17|url-status=dead|archive-url=https://web.archive.org/web/20120510162404/http://energia.gob.mx/res/PE_y_DT/pub/LPG%20Outlook%202008-2017.pdf|archive-date=2012-05-10}}</ref>