{
  "url": "https://openlegislation.uk/eu-regulation-2017-654/annex-VII/division-3/division-3.3/division-3.3.2/division-3.3.2.1",
  "json_url": "https://openlegislation.uk/eu-regulation-2017-654/annex-VII/division-3/division-3.3/division-3.3.2/division-3.3.2.1.json",
  "legislation": "eur/2017/654",
  "legislation_title": "Commission Delegated Regulation (EU) 2017/654 of 19 December 2016 supplementing Regulation (EU) 2016/1628 of the European Parliament and of the Council with regard to technical and general requirements relating to emission limits and type-approval for internal combustion engines for non-road mobile machinery",
  "legislation_url": "https://openlegislation.uk/eu-regulation-2017-654",
  "path": "annex/VII/division/3/division/3.3/division/3.3.2/division/3.3.2.1",
  "kind": "division",
  "number": "3.3.2.1",
  "heading": "Vapour pressure of water",
  "text": "The vapour pressure of water p H2O [kPa] for a given saturation temperature condition, T sat [K], shall be calculated by means of equations (7-77) or (7-78):\n(a) For humidity measurements made at ambient temperatures from 0 to 100 °C or for humidity measurements made over super-cooled water at ambient temperatures from – 50 to 0 °C:\nlog 10 p H2O = 10,79574 × 1 − 273,16 T sat − 5,02800 × log 10 T sat 273,16 + 1,50475 × 10 − 4 × 1 − 10 − 8,2969 × T sat 273,16 − 1 + 0,42873 × 10 − 3 × 10 4,76955 × 1 − 273,16 T sat − 1 − 0,2138602\n(7-77)\nWhere:\np H2O vapour pressure of water at saturation temperature condition [kPa]\nT sat saturation temperature of water at measured condition [K]\n(b) For humidity measurements made over ice at ambient temperatures from (– 100 to 0) °C:\nlog 10 p H2O = − 9,096853 × 273,16 T sat − 1 − 3,566506 × log 10 273,16 T sat + 0,876812 × 1 − T sat 273,16 − 0,2138602\n(7-78)\nWhere:\nT sat saturation temperature of water at measured condition [K]",
  "extent": "E+W+S+N.I.",
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/eur/2017/654/annex/VII/division/3/division/3.3/division/3.3.2/division/3.3.2.1",
    "retrieved_at": "2026-11-01T14:45:01.864924+00:00"
  },
  "licence": "Open Government Licence v3.0",
  "licence_url": "https://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/",
  "attribution": "Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives."
}