{
  "url": "https://openlegislation.uk/heathrow-airportlondon-noise-insulation-grants-scheme-1989/schedule/paragraph-8",
  "json_url": "https://openlegislation.uk/heathrow-airportlondon-noise-insulation-grants-scheme-1989/schedule/paragraph-8.json",
  "legislation": "uksi/1989/247",
  "legislation_title": "The Heathrow Airport–London Noise Insulation Grants Scheme 1989",
  "legislation_url": "https://openlegislation.uk/heathrow-airportlondon-noise-insulation-grants-scheme-1989",
  "path": "schedule/paragraph/8",
  "kind": "paragraph",
  "number": "8",
  "heading": "Specification for permanent vents",
  "text": "(1) Every permanent vent type “A” shall consist of a sound attenuating purpose-made opening or duct which is designed to allow the passage of air between the room and the external air at all times, and shall have an external cowl or grill for protection against the passage of snow, rain and vermin. It shall be so constructed that when installed in a cavity wall exposed to the weather the weather resistance of the cavity is retained and the acoustic performance of the vent is protected.\n(2) The effective area of the air path through the permanent vent shall be ascertained by the method set forth in paragraph 7 (7) above, save that for the words “ventilator system” there shall be substituted “permanent vent”.\n(3) When installed the permanent vent shall be securely fixed to the wall and the junction between the vent and the face of the wall shall be fully sealed by means of compressible strip mastic packing, cover strips or other equally effective means, and where the vent has an air supply duct traversing a cavity wall the junction between the supply duct and the internal leaf shall be fully sealed by suitable means to prevent the passage of air to or from the cavity.\n(4) Vents shall be so constructed and installed as not to present a fire hazard.\n(5) Every permanent vent type “A” shall:\n(a) have an effective area, calculated in accordance with paragraph (2) above, of not less than 3,250 square millimetres, and\n(b) be so constructed that the sound pressure level difference ascertained by the method set forth in paragraph 7(8)(b) above, complied with the requirements therein set forth, save that for the words “ventilator unit” there shall be substituted “vent”.",
  "extent": null,
  "status": null,
  "version": "current",
  "annotations": [],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/uksi/1989/247/schedule/paragraph/8",
    "retrieved_at": "2026-10-29T15:49:39.256906+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."
}