Hazardous Waste Class 4: Flammable Solids

Flammable solids can create potential threats for industries that use them. 

That’s why if you’re a company that uses any of the substances considered to be a Class 4 Hazardous Waste, it’s critical to ensure that you have procedures in place for proper storage, use and disposal of these materials so that they do not present a danger to your employees and property.

Below, we’ll explore some of the most frequent questions that address:

  • What Class 4 Flammable Solids are,
  • What you should be aware of when shipping,
  • Why compliance is critical,
  • Why it’s important to dispose of them properly.


What are Class 4: Flammable Solids?


Any solid that readily begins a combustion process with the help of an igniter classifies as a flammable solidsClass 4 Flammable Solid.

Class 4 materials undergo combustion without outside changes to density or pressure. They are also prone to combustion without the assistance of chemical accelerants. 

The U.S. Department of Transportation breaks this hazard class into three general categories:

  • 4.1 Flammable Solids
  • 4.2 Spontaneously Combustible
  • 4.3 Water Reactive


4.1 Flammable Solids


This type of Class 4 hazardous waste is easily ignitable or may contribute to a fire when friction occurs. These include:

  • Flammable solids
  • Self-reactive substances
  • Solid desensitized explosives

Examples of this category include nitrocellulose and magnesium. These dangerous materials are marked with a red and white vertically striped DOT placard featuring a flame symbol.


4.2 Spontaneously Combustible 


These materials are liable to the spontaneous generation of heat. This can occur during transportation, which can then lead to a fire. Spontaneously combustible materials include:

  • Pyrophoric substances
  • Self-heating substances

Examples of this category include aluminum alkyls and white phosphorus. This placard is white on the top half and features a flame symbol, and red on the bottom half with the words “Spontaneously Combustible.”


4.3 Water Reactive


These substances are dangerous when wet. When they come in contact with water, they emit a flammable gas or react violently.

Examples of this category include sodium, calcium, potassium and calcium carbide. The placard associated with this substance is blue and features a flame symbol.


What Should I Know About Shipping Flammable Solids?


As a hazardous waste generator, you are responsible for any cradle-to-grave requirements, flammable solidsincluding during shipping and disposal of your flammable solids.

As part of these requirements, you’ll need to ensure during transportation your shipment includes:

  • A shipping manifest: In 2018, the Environmental Protection Agency began implementing a national e-manifest system that tracks hazardous waste shipments electronically. 
  • The proper hazardous waste labels: The DOT requires hazardous waste generators to label and mark each package of waste before transporting off-site. The Class 4 labels are outlined in the above section.
  • California requirements: The California Department of Toxic Substances Control (DTSC) also provides its own set of requirements that generators must follow, including:
    • The composition and physical state of the waste
    • A statement that calls attention to the hazardous properties of the waste
    • Name and address of the generator

Working with a certified hazardous waste management firm with a wide breadth of experience will help ensure that any materials you have are properly transported. This is especially important if you are transporting more than one different type of substance since some materials cannot be loaded, transported or stored together in the same transport vehicle.


Why Is Compliance Important?


If your business works with Class 4 Flammable Solids, it’s important to make sure they are transported and disposed of properly. Not doing so can be costly - to the point where your business may not survive

Offering comprehensive training programs for employees who are exposed to these flammable solids can help promote the highest safety standards in the workplace. 

We recommend that you work with an experienced hazardous materials services company to:

  • Ensure you are in compliance with all state and federal regulations.
  • Avoid hefty fines, liability from danger, and injury to your employees and others.
  • Properly transport and dispose of hazardous wastes and non-hazardous wastes. 

It’s also important to work with a company that provides a 24-hour hazmat emergency response should an emergency occur involving Class 4 Flammable Solids. One chemical waste management facility found out the hard way that failing to report spills, even if no danger is posed to nearby communities or workers in your facility, can lead to costly fines.


Why Dispose Of Professionally?


The disposal of Class 4 Flammable Solids is managed by federal and state laws. The U.S. flammable solidsDepartment of Transportation, EPA, and the California DTSC prohibit these types of substances from being disposed of as normal waste.

That’s because these substances are either easily ignitable or can combust when exposed to another element or environment. It is important to limit your organization’s liability and expenses.

A reputable hazardous waste management firm will protect your employees and company by:

  • Keeping you in regulatory compliance
  • Ensuring all transportation requirements are met
  • Guaranteeing the appropriate shipping manifests are completed
  • Properly dispose of your waste
  • Keeping up with changing state and federal regulations

You can read more about how a hazardous waste transportation and disposal company will help you manage your Class 4 Flammable Solids waste by reading our article, How A Hazardous Waste Management Company Protects Your Bottom Line.


Bottom Line


If you are a hazardous waste generator, especially one that produces Class 4 waste, it’s important to understand flammable solids before they cause a hazardous waste emergency.

Companies that work with Class 4 materials should develop a comprehensive transportation and disposal strategy, as the results of improperly disposed of flammable solids could be disastrous.

Failure to remove these substances properly increases the risk of environmental contamination and fire damages. Full-service hazardous waste companies offer responsible disposal and emergency response services that help ensure you stay in compliance while allowing you to focus on day-to-day operations.


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