Fire risk often plays a large role in determining how flammable liquids are stored. Knowing how your flammable liquids are classified will help you determine that fire risk. 

What class is flammable liquids in? The National Fire Protection Association (NFPA) classifies all flammable liquids as Class I. This class is then broken down into six categories, known as sub-classifications, based on the risk of fire. These six flammable liquids categories are:

1. Class IA

2. Class IB

3. Class IC

4. Class III

5. Class IIIA

6. Class IIIB 

If your facility houses flammable liquids, it’s extremely important to know which category your liquid falls under and their flash points, since this information impacts storage requirements in two ways: 

1. Container Size

2. Maximum Quantities 

Below we’ll explain what the NFPA classification system is based on and how that impacts which category a flammable liquid falls in, as well as any storage requirements that are impacted by this sub-classification.


Flammable Liquids Categories


The NFPA classification system is based on a liquid’s flash point.  

What is a flash point? A flash point is, “the lowest temperature at which a substance generates a sufficient amount of vapor to form a vapor/air mixture that can be ignited.”  

Flammable liquids, which catch on fire and easily burn at normal working temperatures, have a flash point under 100 degrees F. Combustible liquids, which need heat before they can ignite, have a flash point at or above 100 degrees. The lower the flash point, the easier the vapors of the liquid will ignite.  

Flammable liquids are categorized based on these flash points, as you can see in the table below:


Flammable Liquids

Combustible Liquids

Class IA

Class III

- Flash points below 73 degrees F

- Flash point at or above 100 degrees F, but below  140 degrees F     

- Boiling points below 100 degrees F

- Examples include camphor oil, diesel fuel, pine tar, motor oil, kerosene

- Unstable flammable liquids also fall under this classification

Class IIIA

- Examples include Ethylene oxide,     pentane, propylene oxide, vinyl           chloride

- Flash point at or above 140 degrees F, but below 200 degrees F

Class IB

- Examples include formaldehyde,    creosote oil, linseed oil, mineral oil

- Flash points below 73 degrees F

Class IIIB

- Boiling points at or above 100 degrees F

- Flash point at or above 200 degrees F

- Examples include acetone, ethyl       alcohol, isopropyl alcohol, benzene,   octane, methanol, heptane

- Examples include castor oil, coconut oil, fish oil, olive oil, ethylene glycol, glycerine

Class IC


- Flash points at or above 73 degrees F, but below 100 degrees F


- Examples include diethylene glycol, turpentine, xylene, isobutyl alcohol, mineral spirits





       Note: According to the NFPA, because Class IA liquids are so volatile, boiling points are                            used only to distinguish between IA and IB.


 Guidelines may vary based on flash points, which is why it’s a good idea to check all local, state and federal regulations. Some regulatory bodies also feature slightly different guidelines. For example, according to the Resource Conservation and Recovery Act, the regulatory cutoff for D001 ignitable liquids is 140 degrees F. D001 is the EPA characteristic waste code that designates a waste stream as ignitable. 


1st Way Classification Impacts Storage: Container Size


There are several general best practices for storing flammable liquids, such as “never block entrances” and “keep away from ignition sources.”  

However, the category your flammable liquid falls under can also subject it to additional, more detailed regulations. For example, the State of California requires specific container sizes for flammable and combustible liquids allowed in laboratories. 


flammable liquids categories

                          Source: UC San Diego


As you can see in the table above, a glass container can only hold 1 pint of a Class IA liquid. However, a glass container can hold 1 gallon of a Class IC liquid. A metal container can only hold 1 gallon of a Class IA liquid, yet can hold 5 gallons of a liquid that falls into any of the other sub-classifications. 

There are some exceptions to these rules that should be noted. For example, glass or approved plastic containers can be used up to 1 gallon in size for flammable liquids if the substances corrode metal containers.


2nd Way Classification Impacts Storage: Maximum Quantity


Classification also impacts the maximum quantity of a material that may be stored in a facility, per California Fire Code. 


flammable liquids categories

                    Source: UC San Diego


The table above shows how flashpoints play a role in determining the total maximum quantity allowed of flammable and combustible liquids in a facility. The California Fire Code breaks down maximum quantities into four categories based on flashpoints.  

These guidelines then impact storage quantities. For example, category 1 has a flash point below 73.4 degrees F and an initial boiling point at or below 95 degrees F. Facilities cannot store more than 10 gallons of any liquid that falls in this category outside of flammable liquid storage cabinets.


Flammable Liquids Disposal 


Flammable Liquids CategoriesStoring any amount of flammable liquids on site can pose several risks. If your facility routinely approaches maximum quantity levels as well, you have the legal responsibility to safely dispose of your hazardous waste in order to comply with the law and keep the community safe.  

Today, companies are looking for hazardous waste options that are more sustainable and cost-effective. Particularly with flammable liquids, many companies are partnering with a company like Temarry Recycling that recycles solvents. 

Temarry operates in Southern California and has a state-of-the-art recycling facility just across the U.S.-Mexico border. It’s here that a solvent distillation process is one component of a Closed Loop Recycling system. This keeps materials at their highest value and ensures nothing is wasted.  

Here’s how Closed Loop Recycling works at Temarry: 

  • A waste to energy process begins the closed loop. Organic solids with >5000 BTU are converted to steam. Waste is fed by a conveyor into the primary stage for thermal destruction at 1500 degrees F. All vapors and gases are then directed to secondary thermal treatment at 1500 degrees F.

  • Inorganic solids, or ash, from the primary stage are quenched and fall into an ash hopper. Heat is then directed to a 200-horsepower steam generator. The remaining gases are directed to a modern two-stage venturi scrubber to ensure that only clean water vapor is emitted into the atmosphere. 

  • The solvent distillation begins next. Using the steam from the waste to energy process as energy to power the recovery stills, spent solvents are re-manufactured and sold back into industry for their original solvent properties. 

  • A water treatment process is needed to close the loop. The water treatment process extracts usable water from industrial hazardous wastes. In turn, treated water is used on site for industrial needs, including the waste-to-energy equipment and a cooling tower.  

Partnering with Temarry can offer many benefits for companies that regularly utilize flammable liquids, especially those located on the West Coast. Companies can save substantial money in transportation costs alone from not having to transport their hazardous waste across the country to the closest cement kilns. They can also lower their carbon footprints since less fuel is needed for transportation.


Know Your Category … And Your Impact


Knowing the category your flammable liquids fall under is important when understanding the risk your hazardous waste poses and what regulations you must follow. These state and federal classifications offer a glimpse into these risks and what can happen if these regulations are not followed. 

However, knowing your flammable liquids categories and any storage requirements associated with these categories are only part of a greater picture. Following what happens to your waste once it leaves your facility plays a significant role in your company’s long-term sustainability outlook. 

Are you Recycling or Fuel Blending

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