Flammable Liquids Classes & Categories

July 30, 2019

Flammable Liquid Categories from the Occupational Safety and Health Administration (OSHA)

OSHA is a bit different. After the changes to the U.S. Labor Law in 2012, OSHA no longer calls any liquids “combustible”.

They refer to any liquid with a closed-cup flash point below 200°F (93°C) as a “flammable liquid”.

This will be most obvious in OSHA’s CFR29 1910.106 and CFR29 1926.152 where the regulations for flammable liquid handling and storage exist.

OSHA Flammable Liquid Types
Type	Flash Point Range
Flammable Liquids	< 200°F (93°C)

There are four flammable liquid categories:

Category 1

Category 2

Category 3

Category 4

Category 1 Flammable Liquids

A Category 1 flammable liquid is any liquid with a closed-cup flash point below 73.4°F (23°C) AND with a boiling point below 95°F (35°C).

Examples of Category 1 Flammable Liquids include:

Diethyl Ether
Pentane
Ligroin
Heptane
Petroleum Ether

Category 2 Flammable Liquids

A Category 2 flammable liquid is any liquid with a closed-cup flash point below 73.4°F (23°C) AND with a boiling point above 95°F (35°C).

Examples of Category 2 Flammable Liquids include:

Acetone
Benzene
Cyclohexane
Isopropyl alcohol
Methyl ethyl ketone
Toluene
Ethanol

Category 3 Flammable Liquids

A Category 3 flammable liquid is any liquid with a closed-cup flash point at or above 73.4°F (23°C) AND below 140°F (60°C).

Category 3 has a caveat.

*When a Category 3 liquid with a flash point at or above 100°F (37.8°C) is heated for use to within 30°F (16.7°C) of its flash point, it shall be handled in accordance with the requirements for a Category 3 liquid with a flash point below 100°F (37.8°C).

Examples of Category 3 Flammable Liquids include:

Xylene
Naphtha
Turpentine
Camphor Oil
Diesel Fuel
Pine Tar
Stoddard Solvent

Category 4 Flammable Liquids

A Category 4 flammable liquid is any liquid with a closed-cup flash point at or above 140°F (60°C) AND below 200°F (93°C).

Category 4 has a caveat as well.

*When a Category 4 flammable liquid is heated for use to within 30°F (16.7°C) of its flash point, it shall be handled in accordance with the requirements for a Category 3 liquid with a flash point at or above 100°F (37.8°C). When liquid with a flash point greater than 199.4°F (93°C) is heated for use to within 30°F (16.7°C) of its flash point, it shall be handled in accordance with the requirements for a Category 4 flammable liquid.

And another chart for the visual learners breaking down the OSHA flammable liquid categories.

[DOWNLOAD] PDF: FLAMMABLE LIQUID CATEGORIES CHART

FLAMMABLE LIQUID CATEGORY CHART (OSHA)

When to Use NFPA’s Flammable Liquid Classes or OSHA’s Flammable Liquid Categories

As you have seen, fire codes are communicated as flammable liquid class IA, IB, IC, II, IIIA, & IIIB; whereas the U.S. Labor Law is communicated as flammable liquid category 1, 2, 3 & 4.

This classification system is VERY confusing and can lead to very dangerous situations if construed incorrectly.

Some advice to help prevent any mix-ups goes back to the old adage for relationship advice:

COMMUNICATION IS KEY!

Make sure that you clearly identify which class or category you are referring to – maybe even specify fire code or OSHA. The clearer communication, the safer everyone will be.

And to make it even EXTRA clear – we created this chart that combines both flammable liquid fire code classes and OSHA categories.

Feel free to bookmark or download for your own reference.

[DOWNLOAD] PDF: FLAMMABLE LIQUID CATEGORIES CHART

Classification of Flammable Liquids
(OSHA & NFPA)

Can You Describe the Difference Between Flammable liquid Classes and Categories Now?

Let’s review.

NPFA Flammable Liquids Class

Flammable liquid classes are designated by the National Fire Protection Agency (NFPA) and there are six classes total based on a liquid’s closed-cup flash point and boiling point: Class IA, Class IB, Class IC, Class II, Class IIIA, and Class IIIB.

These six classes fall into either flammable liquids or combustible liquids.

OSHA Flammable Liquids Category

Flammable liquid categories are specified by the Occupational Safety and Health Administration (OSHA). There are four categories also based on a liquid’s closed-cup flash point and boiling point: Category 1, 2, 3, & 4.

All four categories are considered flammable liquids and none are labeled as combustible liquids.

And Don’t Forget…

The temperatures for each section DO NOT CORRELATE evenly between fire code classes and OSHA categories.

Pay attention to which laws you need to adhere to in each situation and make sure you are referencing the correct class or category.

Perhaps the biggest takeaway from this article is that communication is key in any industry that deals with flammable liquids.

Not only are there complicated classifications for flammable liquids, but it also gets even more convoluted on how you are supposed to handle and store each class or category of flammable liquids.

Don’t worry, we’ve got you covered.

The next upcoming article in this topic is all about flammable liquid storage rules for small quantities, and if you are thinking on a larger scale – we will lay out all of the rules and regulations for a hazardous materials warehouse that is coded and approved for flammable liquids.

Stay tuned…

[DOWNLOAD] PDF: FLAMMABLE LIQUID CATEGORIES CHART

Disclaimer:

All content on this website is for informational purposes only. This information should not be considered complete, up to date, and is not intended to be used in place of the consultation or advice of a legal, medical, or any other professional. Chemical Strategies, Inc. assumes no responsibility or liability for any errors or omissions in the content of this site. We do not make any warranties about the completeness, reliability, and accuracy of this information. You use all information at your own risk.

Have you ever tried to find a certain flammable liquids class?

You have probably noticed that there is some confusion in this area. Some regulations refer to flammable liquid “classes”, while others refer to flammable liquid “categories”.

To clear it up for you right now – there are both. The National Fire Protection Association (NFPA) has established flammable liquids classes:

Class IA
Class IB
Class IC
Class II
Class IIIA
Class IIIB

Due to some updates to U.S. Labor Law in 2012, the Occupational Safety and Health Administration (OSHA) amended 29 CFR1910.106 and 29 CFR1926.152 with new definitions of what a flammable liquid is and now refer to flammable liquids categories:

Category 1
Category 2
Category 3
Category 4

We will get more into the specifics, but both the flammable liquid classes and categories are extremely important.

After breaking down each flammable liquid class and category and looking at real-life examples of each, any confusion will be cleared right up.

TOPICS:

Flammable Liquid Classes from the National Fire Protection Association (NFPA)
Flammable Liquid Categories from the Occupational Safety and Health Administration (OSHA)
[CHART] Flammable Liquid Classes & Categories
When to Use NFPA’s Flammable Liquid Classes or OSHA’s Flammable Liquid Categories
Difference Between Flammable Liquid Classes and Categories

[DOWNLOAD] PDF: FLAMMABLE LIQUID CATEGORIES CHART

Flammable Liquid Classes from the National Fire Protection Association (NFPA)

The core laws set by NFPA in regard to flammable and combustible liquids include the IFC International Fire Codes©, NFPA® 1 Fire Code, and NFPA® 30 Flammable and Combustible Liquids Code. NFPA splits flammable liquids into two types: flammable and combustible.

According to NFPA, a flammable liquid is a liquid with a closed-cup flash point less than 100°F (38°C). A combustible liquid is a liquid with a closed-cup flash point greater than or equal to 100°F (38°C).

NFPA Flammable Liquid Types
Type	Flash Point Range
Flammable Liquids	< 100°F (38°C)
Combustible Liquids	≥ 100°F (38°C)

These definitions are fairly broad, so NFPA established further subcategories of six classes.

Those flammable liquid classes are:

Class IA

Class IB

Class IC

Class II

Class IIIA

Class IIIB

Keep in mind that the LOWER the flash point the MORE HAZARDOUS a substance is because it is flammable at a lower temperature. So Class IA is the most volatile.

Let’s breakdown the details of each class with some examples.

Class IA Flammable Liquids

A Class IA flammable liquid is any liquid with a closed-cup flash point below 73°F (23°C) AND with a boiling point below 100°F (38°C).

Examples of Class IA Flammable Liquids include:

Diethyl Ether
Pentane
Ligroin
Petroleum Ether

Class IB Flammable Liquids

A Class IB flammable liquid is any liquid with a closed-cup flash point below 73°F (23°C) AND with a boiling point at or above 100°F (38°C).

Examples of Class IB Flammable Liquids include:

Acetone
Benzene
Cyclohexane
Isopropyl Alcohol
Methyl Ethyl Ketone
Toluene
Ethanol
Heptane

Class IC Flammable Liquids

A Class IC flammable liquid is any liquid with a closed-cup flash point at or above 73°F (23°C) and below 100°F (38°C).

Examples of Class IC Flammable Liquids include:

Xylene
Naphtha
Turpentine

Now we start to get into the transition from flammable liquid to combustible liquids according to NFPA’s definitions.

Class II Combustible Liquids

A Class II combustible liquid is any liquid with a closed-cup flash point at or above 100°F (38°C) and below 140°F (60°C).

Examples of Class II Combustible Liquids include:

Camphor Oil
Diesel Fuel
Pine Tar
Stoddard Solvent

Class IIIA Combustible Liquids

A Class IIIA combustible liquid is any liquid with a closed-cup flash point at or above 140°F (60°C) and below 200°F (93°C).

Examples of Class IIIA Combustible Liquids include:

Aniline
Benzaldehyde
Butyl Cellosolve
Nitrobenzene
Pine Oil
Formaldehyde

Class IIIB Combustible Liquids

A Class IIIB combustible liquid is any liquid with a closed-cup flash point at or above 200°F (93°C).

Examples of Class IIIB Combustible Liquids include:

Animal Oils
Ethylene Glycol
Glycerin
Lubricating
Quenching
Transformer Oils
Triethanolamine
Benzyl Alcohol
Hydraulic Fluids
Vegetable Oils

Here is a chart for all of you visual learners that explains the different NFPA flammable liquid classes. Download Chart.

FLAMMABLE LIQUID CLASS CHART (NFPA)

Flammable Liquid Categories from the Occupational Safety and Health Administration (OSHA)

OSHA is a bit different. After the changes to the U.S. Labor Law in 2012, OSHA no longer calls any liquids “combustible”.

They refer to any liquid with a closed-cup flash point below 200°F (93°C) as a “flammable liquid”.

This will be most obvious in OSHA’s CFR29 1910.106 and CFR29 1926.152 where the regulations for flammable liquid handling and storage exist.

OSHA Flammable Liquid Types
Type	Flash Point Range
Flammable Liquids	< 200°F (93°C)

There are four flammable liquid categories:

Category 1

Category 2

Category 3

Category 4

Category 1 Flammable Liquids

A Category 1 flammable liquid is any liquid with a closed-cup flash point below 73.4°F (23°C) AND with a boiling point below 95°F (35°C).

Examples of Category 1 Flammable Liquids include:

Diethyl Ether
Pentane
Ligroin
Heptane
Petroleum Ether

Category 2 Flammable Liquids

A Category 2 flammable liquid is any liquid with a closed-cup flash point below 73.4°F (23°C) AND with a boiling point above 95°F (35°C).

Examples of Category 2 Flammable Liquids include:

Acetone
Benzene
Cyclohexane
Isopropyl alcohol
Methyl ethyl ketone
Toluene
Ethanol

Category 3 Flammable Liquids

A Category 3 flammable liquid is any liquid with a closed-cup flash point at or above 73.4°F (23°C) AND below 140°F (60°C).

Category 3 has a caveat.

Examples of Category 3 Flammable Liquids include:

Xylene
Naphtha
Turpentine
Camphor Oil
Diesel Fuel
Pine Tar
Stoddard Solvent

Category 4 Flammable Liquids

A Category 4 flammable liquid is any liquid with a closed-cup flash point at or above 140°F (60°C) AND below 200°F (93°C).

Category 4 has a caveat as well.

And another chart for the visual learners breaking down the OSHA flammable liquid categories.

[DOWNLOAD] PDF: FLAMMABLE LIQUID CATEGORIES CHART

FLAMMABLE LIQUID CATEGORY CHART (OSHA)

When to Use NFPA’s Flammable Liquid Classes or OSHA’s Flammable Liquid Categories

As you have seen, fire codes are communicated as flammable liquid class IA, IB, IC, II, IIIA, & IIIB; whereas the U.S. Labor Law is communicated as flammable liquid category 1, 2, 3 & 4.

This classification system is VERY confusing and can lead to very dangerous situations if construed incorrectly.

Some advice to help prevent any mix-ups goes back to the old adage for relationship advice: