Reportable quantity (RQ)

Each listed substance has its own RQ, reflecting how serious a release would be. A highly hazardous substance may have a small RQ, while a less harmful one may have a larger value. When a release in a 24-hour period reaches or exceeds the RQ, the person in charge must notify the National Response Center without delay.

RQs come mainly from CERCLA, but EPCRA also uses them for extremely hazardous substances, requiring release notice to state and local emergency planners. The Clean Water Act has its own related reporting of oil and hazardous substance discharges. A single event can trigger several notices.

For a mixture, the RQ relates to the quantity of each listed component, not the total weight of the product. That means a spill of a dilute solution may or may not meet the threshold. The calculation is easiest if the SDS gives component percentages.

The Department of Transportation also uses RQs. If a package contains a quantity of a hazardous substance at or above its RQ, shipping papers and markings must carry extra identification. This is separate from the release-reporting duty but uses the same list.

Reporting a release does not by itself assign blame. It lets responders assess risk. Failure to report, however, can bring penalties, and the facility should document the event, quantities, and actions taken.