How To Work Safely With Flammable and Combustible Liquids

by | | 0 comment(s)
How To Work Safely With Flammable and Combustible Liquids

Flammable and combustible liquids are exceptionally dangerous fire hazards because they can ignite and spread quickly. Below, we’ll go over flammable and combustible liquids and what every workplace and worker needs to know to work safely with them.

Flammable & Combustible Liquids Defined

First, to know the best practices for safely managing flammable and combustible liquids, we must understand what they are. Flammable liquids are any liquids with a flashpoint of 100 degrees Fahrenheit or less. A combustible liquid has a flashpoint above 100 degrees F.

These parameters for combustible and flammable liquids are for the general industry and are slightly different for the construction industry due to the uniqueness of the setting.

Classes of Flammable Liquids

Within flammable liquids are classes that help categorize them from most dangerous to least dangerous. The classes range from 1-A to 1-C, with 1-A being the most dangerous.

Class 1-A Flammable Liquid: Liquid substance with a flashpoint below 73 degrees F and a boiling point below 73 degrees F.

Examples: Diethyl ether and petroleum ether

Class 1-B Flammable Liquid: Liquid substance with a flashpoint below 73 degrees F and a boiling point above 100 degrees F.

Examples: Acetone and benzene

Class I-C Flammable Liquid: Liquid substance with a flashpoint between 73 and 100 degrees F.

Examples: Turpentine and butyl alcohol

Classes of Combustible Liquids

Combustible liquids also have classes—Class II, III-A, and III-B, with II being the most dangerous and III-B being the least dangerous.

Class II Combustible Liquid: Liquid substance with a flashpoint between 101 and 140 degrees F.

Examples: Motor oil and kerosene

Class III-A Combustible Liquid: Liquid substance with a flashpoint between 141 and 199 degrees F.

Examples: Linseed and mineral oil

Class III-B Combustible Liquid: Liquid substance with a flashpoint above 200 degrees F.

Examples: Oil-based paints and coconut oil

Key Terms To Know for Flammable & Combustible Liquids

To understand the details of flammable and combustible liquid safety, there are some key terms that every worker and manager at an industrial workplace should know and understand.

Ignition Source

An ignition source is anything capable of igniting flammable or combustible liquids or fumes. What makes ignitions sources dangerous is that they can come from practically anywhere and include:

  • Open flames
  • Sparks
  • Hot surfaces
  • Faulty electrical wiring


As one can see, the classification of combustible and flammable liquids depends primarily on its flashpoint. The flashpoint is the lowest temperature at which an ignition source can ignite the vapors of a liquid substance.

While the flashpoint temperature can cause a liquid substance to ignite, it doesn’t mean it will continue to combust if the ignition source gets removed. The lower the flashpoint, the more flammable and dangerous a substance is.


Vapors are a primary concern for flammable and liquid substance safety primarily due to the possibility of flashbacks. Flashback is when a liquid substance’s vapors ignite, and the flame travels back to the source and causes massive combustion.

Flashback can occur even if the source of the vapors is hundreds of feet away or even on another level of the building without sufficient precautions.

Auto-Ignition Temperature

The auto-ignition temperature is like the flashpoint of a flammable or combustible substance. Once a substance reaches its auto-ignition temperature, the vapor-air mixture can spontaneously combust without an ignition source.

This temperature is much higher than the flashpoint but exceptionally more dangerous.

Vapor Pressure

The vapor pressure is a measure of the liquid’s volatility. The higher the vapor pressure of a substance, the more ready it is to vaporize—produce flammable and toxic fumes quickly.

The more vapors emanating from a flammable substance, the greater the danger—so, the higher the vapor pressure, the more dangerous it is.

What’s Needed To Handle Flammable & Combustible Liquids Safely

Now that we have a firm understanding of these substances and their dangers, we can understand that workplaces and employees need to work safely with flammable and combustible liquids.

Ignition Source Control

The last thing that any workplace or worker needs is an ignition source near a flammable or combustible liquid. Unless the liquid substance is at its auto-ignition temperature, it won’t ignite without introducing an ignition source.

But as we mentioned, ignition sources can come in many forms, from open flames to simple static electricity. And as we said with flashback, the ignition source doesn’t even have to be close to the source to cause combustion, so you must take sufficient precautions to limit any potential sources from the workplace.

Safety Training

Knowledge and education are half the battle with handling flammable and combustible liquids. As you can see, there are many things someone working with these substances should know—from their liquid’s vapor pressure to proper handling procedures.

OSHA requires that all employees get trained in safety and handling techniques. The safety training should include emergency extinguishing drills, substance handling precautions, and even seemingly simple things like how to safely lift a drum of a flammable substance with two people.


As discussed, vapors are incredibly dangerous when handling flammable and combustible liquids. Not only can these fumes start fires and combust liquids, but they can be hazardous to the health and safety of the workers.

Ventilation is a requirement for any setting that stores or handles these dangerous substances. Without proper ventilation, vapors can build and spread and cause combustion through flashback.

Automatic Extinguishing System

Another requirement for any workplace containing flammable and combustible liquids is an automatic extinguishing system as part of the OSHA Standard regarding flammable liquids. These are strict regulations, and any workplace not compliant with the standard could face significant consequences and put workers at risk.

Since fires from flammable and combustible liquids can start and spread so quickly due to their low flashpoint, every second counts. An automatic extinguishing system will react much faster than a worker can in deploying extinguishing measures to quench the fire as soon as possible.

Personal Protective Equipment (PPE)

Along with the proper procedures and training, workers need sufficient protective personal equipment to guard against injury. Flame-resistant clothing protects against flame and thermal injuries should a worker encounter a fire.

Some flame-resistant uniforms are one-piece jumpsuits for total protection, while others can be more casual, like a flame-resistant sweatshirt and flame-resistant pants. Along with protective clothing, workers should have eye protection, non-absorbent gloves, and a facial covering to prevent significant inhalation of toxic vapors.


As you can see, a lot goes into safely handling these volatile and dangerous liquid substances. If you or your workers require additional PPE or flame-resistant uniforms, FR Outlet has an expansive inventory of protective garments and accessories.

This entry was posted in no categories.

You must be logged in to post comments.