The number that matters is not the same for everything
Most chemicals become reportable when you hold 10,000 pounds at once. A short federal list — extremely hazardous substances — starts far lower, at 500 pounds or its own planning quantity, whichever is smaller. Some solids have two numbers depending on their form.40 CFR 370.10
Pounds, not gallons — so a liquid has to be converted before it can be compared, and the density you use changes the answer. Each page below says which number applies and where it came from.
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Oil and fuels
These carry a second rule with them. Above 1,320 gallons of storage above ground, a site where a spill could reach water needs a written spill plan, and that line sits below the Tier II one.
Everything else
Gases, acids, batteries and the rest. Some of these are extremely hazardous and start at a much lower number than you would expect.
Not on this list? The free checker searches EPA’s full List of Lists — 1,975 substances — by name or CAS number.