{"data":{"id":"us/40-cfr-1065.644","jurisdiction":"us","citation":"40 CFR 1065.644","heading":"Vacuum-decay leak rate.","body":"This section describes how to calculate the leak rate of a vacuum-decay leak verification, which is described in § 1065.345(e). Use the following equation to calculate the leak rate, , and compare it to the criterion specified in § 1065.345(e):\nEq. 1065.644-1\nWhere:\nVvac = geometric volume of the vacuum-side of the sampling system.\nR = molar gas constant.\np2 = vacuum-side absolute pressure at time t2.\nT2 = vacuum-side absolute temperature at time t2.\np1 = vacuum-side absolute pressure at time t1.\nT1 = vacuum-side absolute temperature at time t1.\nt2 = time at completion of vacuum-decay leak verification test.\nt1 = time at start of vacuum-decay leak verification test.\nExample:\nVvac = 2.0000 L = 0.00200 m 3\nR = 8.314472 J/(mol·K) = 8.314472 (m 2·kg)/(s 2·mol·K)\np2 = 50.600 kPa = 50600 Pa = 50600 kg/(m·s 2)\nT2 = 293.15 K\np1 = 25.300 kPa = 25300 Pa = 25300 kg/(m·s 2)\nT1 = 293.15 K\nt2 = 10:57:35 a.m.\nt1 = 10:56:25 a.m.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER U—AIR POLLUTION CONTROLS","PART 1065—ENGINE-TESTING PROCEDURES","Subpart G—Calculations and Data Requirements"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"b0b5231b2837a56f4d2df725a0c6a3c3e736ece001e6f0c2cfcd6407035922c2","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-1065.643","next":"us/40-cfr-1065.645"},"notice":"GroundRules: Original legal text. Not legal advice."}