Arguably the most notable change within the Ignitability of Hazardous Waste’s new and final rule is the accepted use of non-mercury thermometers as an allowable flashpoint test method under Title 40, Code of Federal Regulations (40 CFR 260.11). Additionally, the rule updates language for the exclusion of aqueous solutions, clarifies requirements for multiphase material testing, and incorporates modern standards into the ignitability characteristic rule.

Recognizing the outdated and potentially toxic testing methods, the Environmental Protection Agency (EPA) obtained feedback from industry professionals, state officials and the public to update how the hazardous waste characteristic of ignitability is determined under the Resource Conservation and Recovery Act (RCRA).

On June 8, 2020, the EPA signed the final rule — Modernizing Ignitable Liquids Determinations — allowing the use of non-mercury thermometers as an alternative sampling method and modifying definitions to match those of other federal agencies’ rulings. These updates, which are mainly informational and provide clarity to existing language, were published in the Federal Register on July 7, 2020. The final rule becomes effective Sept. 8, 2020.

For solid waste to be classified and regulated as hazardous waste, it has to explicitly be listed as such or exhibit a “characteristic” property of hazardous waste: ignitability, corrosivity, reactivity and toxicity. Under RCRA regulations, liquid wastes with flashpoints less than 140 degrees F (60°C) are considered ignitable — meaning they have the potential to cause harm to human health or the environment through direct or indirect fire hazards. Other regulated ignitable hazardous wastes include:

  • Ignitable compressed gases, such as ethane and butane gas.
  • Nonliquid substances capable of causing fire through friction, absorption of moisture, or spontaneous change or reaction.
  • Oxidizer chemicals, such as sodium nitrate, sodium perchlorate and ammonium nitrate.

A Look Into the New Rule

A nontoxic, environmentally friendly addition, non-mercury thermometers now are allowed in a variety of the EPA’s analytical methods that, in the past, required mercury thermometers. Most laboratories already have digital instrumentation for flashpoint testing as required by the American Society of Testing & Materials (ASTM); however, the ability to use non-mercury thermometers is now officially codified in the regulations.

The final rule covers a few text and technical changes as well. Within the existing rule, there’s an exclusion for “aqueous solutions” containing less than 24% alcohol by volume. Under the final rule, this definition clarifies the meaning of “aqueous,” defining it as “at least 50% water by weight.” Other minor technical changes include clarification of the requirements for testing multiphase materials; a new ASTM standard for compressed gas testing, which is a proven test method used by the Department of Transportation (DOT); and an updated oxidizer definition that replaces obsolete references to DOT regulations.

Its Effect Within Each State

Virtually all states have their own authorized hazardous waste regulatory programs. In the preamble to the final rule, EPA acknowledges that the changes to the ignitability characteristic will not take effect in such authorized states unless and until the states adopt the changes. EPA further states that because the changes are “neither more nor less stringent” than the preexisting rules, states will not be required to adopt them.

Though this rule update doesn’t significantly impact daily operations or affect proper management of hazardous waste on-site, it’s good to be aware of what’s happening industrywide, especially when changes relate to improved safety and health measures. A trusted partner, one who is well-versed in environmental health and safety standards and hazardous waste compliance, can wade through final ruling specifics to bring hazardous waste management plans and testing methods up to speed.


A comprehensive, sustainable compliance program offers a variety of services to confidently navigate the ever-changing regulatory landscape, regardless of how complex it might seem.


Matt Shanahan specializes in hazardous waste management and has more than 20 years of experience in environmental compliance and permitting.