Threshold Planning Quantity

The amount of an Extremely Hazardous Substance at which emergency planning obligations begin.

Each Extremely Hazardous Substance has a Threshold Planning Quantity assigned by EPA, ranging from one pound to 10,000 pounds depending on how hazardous the substance is and its physical form.

Holding an EHS at or above its TPQ triggers notification under Section 302. The TPQ also sets the Tier II reporting threshold for that substance, which is the lower of 500 pounds or the TPQ.

Some substances carry a lower TPQ when present as a fine powder or in solution, because the form affects how readily the substance disperses in a release.

Related terms

• Extremely Hazardous SubstanceA substance on EPA's Section 302 list, subject to lower reporting thresholds and emergency planning notification.
• EPCRA Section 302Requires a facility to notify state and local planners when it holds an Extremely Hazardous Substance at or above its Threshold Planning Quantity.
• Reporting thresholdThe quantity at which a chemical becomes reportable: 10,000 lb for most, lower for Extremely Hazardous Substances.

A plain-English explanation, not legal advice. Figures are the federal baseline; your state may differ, so see the state-by-state requirements.