# The Air Quality (Wales) Regulations 2000, Paragraph 5

Extent: E+W

A 24 hour mean is a mean calculated every 24 hours. The 24 hour mean for a substance at a particular location for a particular 24 hour period is the level at which that substance is recorded as being present in the air at that location on the basis of a continuous sample of air taken throughout the period.

---
Source: https://www.legislation.gov.uk/wsi/2000/1940/schedule/paragraph/5 (the official version)
Page: https://openlegislation.uk/air-quality-wales-regulations-2000/schedule/paragraph-5
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.