# The Dark Smoke (Permitted Periods) Regulations 1958, Regulation 4


Nothing in these regulations shall authorise—
(i) the continuous emission of dark smoke, caused otherwise than by soot-blowing, for a period exceeding 4 minutes; or
(ii) the emission of black smoke for more than 2 minutes in the aggregate in any period of 30 minutes.

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Source: https://www.legislation.gov.uk/uksi/1958/498/regulation/4 (the official version)
Page: https://openlegislation.uk/dark-smoke-permitted-periods-regulations-1958/regulation-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.