{
  "url": "https://openlegislation.uk/air-quality-standards-wales-regulations-2010/schedule-1/paragraph-wrapper1n1",
  "json_url": "https://openlegislation.uk/air-quality-standards-wales-regulations-2010/schedule-1/paragraph-wrapper1n1.json",
  "legislation": "wsi/2010/1433",
  "legislation_title": "The Air Quality Standards (Wales) Regulations 2010",
  "legislation_url": "https://openlegislation.uk/air-quality-standards-wales-regulations-2010",
  "path": "schedule/1/paragraph/wrapper1n1",
  "kind": "paragraph",
  "number": null,
  "heading": null,
  "text": "Sulphur dioxide\nAveraging period\nLimit value\nOne hour\n350 μg/m3, not to be exceeded more than 24 times a calendar year\nOne day\n125 μg/m3, not to be exceeded more than 3 times a calendar year\nNitrogen dioxide\nAveraging period\nLimit value\nOne hour\n200 μg/m3, not to be exceeded more than 18 times a calendar year\nCalendar year\n40 μg/m3\nBenzene\nAveraging period\nLimit value\nCalendar year\n5 μg/m3\nCarbon monoxide\nAveraging period\nLimit value\nMaximum daily eight hour mean\n10 mg/m3\nLead\nAveraging period\nLimit value\nCalendar year\n0.5 μg/m3\nPM10\nAveraging period\nLimit value\nOne day\n50 μg/m3, not to be exceeded more than 35 times a calendar year\nCalendar year\n40 μg/m3\nPM2·5\nAveraging period\nLimit value\nMargin of tolerance\nDate by which limit value is to be met\nCalendar year\n25 μg/m3\n20% on 11 June 2008, decreasing on the next 1 January and every 12 months thereafter by equal annual percentages to reach 0% by 1 January 2015\n1 January 2015",
  "extent": "E+W",
  "status": null,
  "version": "current",
  "annotations": [
    {
      "type": "M",
      "label": "M1",
      "text": "The maximum daily eight hour mean concentration of carbon monoxide must be selected by examining eight hour running averages, calculated from hourly data and updated each hour. Each eight hour average so calculated must be assigned to the day on which it ends, that is, the first calculation period for any one day will be from 17:00 on the previous day to 01:00 on that day, and the last calculation period for any one day will be the period from 16:00 to 24:00 on that day."
    }
  ],
  "outstanding_effects": [],
  "provenance": {
    "source": "legislation.gov.uk",
    "source_url": "https://www.legislation.gov.uk/wsi/2010/1433/schedule/1/paragraph/wrapper1n1",
    "retrieved_at": "2026-10-28T23:53:41.556554+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."
}