Compliance Strategies & Hazardous Materials Management
Friday August 1st 2014

Flammable Liquids vs. Combustible Liquids

It seems that most people today don’t know the difference between a flammable liquid and a combustible liquid.  It is very important to know the difference, especially for those who manufacturer and ship/offer these two liquids for transportation.  Knowing and understanding the difference between the two could be a difference for the bottom line of a company. 

The Department of Transportation (DOT) defines both (flammable liquids & combustible liquids) in Hazardous Materials Regulations (HMR) which are found in Title 49 – Transportation.   All definitions are found in Part 171.8 Definitions and abbreviations.  In our case with comparing these two liquids – we are pushed deeper inside of the HMR.  Reading regulations are as easy as searching it on the web or finding them in a paper copy.  Understanding what the regulations are trying to say is hard for some companies to follow and comply with on a daily basis.  There are many companies who offer their services to help understand government regulations.  Finding the right company – well that’s another story – for another time.

Searching Part 171 for a flammable liquid, it says see Part 173.120.  So moving forward to Part 173, we get the definition. 

Part 173.120(a).  A flammable liquid(Class 3) means a liquid having a flash point of not more tha 60°C (140°F), or any material in a liquid phase with a flash point at or above 37.8°C (100°F) that is intentionally heated and offered for transportation or transported at or above its flash point in a bulk packaging.  The DOT gives 5 exceptions which would make this article very long, so we will cover the highlights of those exceptions.

(1) Any liquid meeting one of the definitions specified in §173.115.

(2) Any mixture having one or more components with a flash point of 60°C (140°F) or higher, that make up at least 99% of the total volume of the mixture, if that mixture is not offered for transportation or transported at or above its flash point.

(3) Any liquid with a flash point greater than 35°C (95°F) that does not sustain combustion according to ASTM D 4206 ( known as the American Society for Testing and Materials) or the procedure in Appendix H of Part 173.

(4) Any liquid with a flash point greater than 35°C (95°F) and with a fire point greater than 100°C (212°F) according to ISO 2592.

(5) Any liquid with a flash point greater than 35°C (95°F) which is in a water-miscible solution with a water content of more than 90% by mass.

Wow – see what I mean when I tell you that the understading government regulations wasn’t easy?

Okay so now let’s take a look at what the DOT says constitutes a liquid to be classified as a combustible liquid.  Once again we find that the DOT pushes from Part 171 to Part 173 for the definition of a combustible liquid.

Part 173.120(b). (1) A combustible liquid means any liquid that does not meet the definition of any other hazard class specified in this subchapter (meaning Class 3 – Definitions) and has a flash point above 60°C (140°F) and below 93° C (200° F).  (2) A flammable liquid with a flash point at or above 38°C (100°F) that does not meet the definition of any other hazard class may be reclassed as a combustible liquid.  Insert a wrench here by the DOT.  It says that we can not do this if we plan on offering this liquid for transportation by vessel or aircraft, except where other means of transportation is impracticable.  The rest of (2) explains  that an elevated temperature material that meets the definition of a Class 3 material because it is intentionally heated and offered for transportation or transported at or above its flash point may not be reclassed as a combustible liquid.  (3)  A combustible liquidthat does not sustain combustion is not subjected to requirements of this subchapter (Class 3 – Definitions) as a combustible liquid.

Making the correct classification of a liquid to determine whether it’s either a flammable liquid or a combustible liquid is very important and key for companies today.  There are many exceptions and exemptions for combustible liquids, which means a cost savings for companies who offer these items.  Not only will companies benefit on the bottom line for proper classification – they will also be compliant with The Department of Transportation, another great way to avoid violations and not pay huge fines increasing their bottom line.

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