Material release threshold quantity
The weight of gas, liquid, or solid material released from an LOPC which, if exceeded, results in the event being recordable as either Tier 1 or Tier 2 PSE. The threshold quantities are described more fully in API/ANSI standard 754 (see Reference 6) and follow the UNDG classification system.
Source: OGP Report No. 456, Process Safety – Recommended Practice on Key Performance Indicators, International Association of Oil & Gas Producers, November 2011. Global Standards