# The Coal Mines (Precautions against Inflammable Dust) Order 1956, Paragraph 1


For the purposes of regulation five the minimum percentage of incombustible matter in relation to any coal shall be determined by reference to the volatile matter content of that coal calculated on an ash-free dry basis in accordance with the following table—
Volatile matter content of coal (Per cent.)
Minimum percentage of incombustible matter required
Not exceeding
20
50
22
55
25
60
27
65
30
68
32
70
35
72
Exceeding
35
75

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Source: https://www.legislation.gov.uk/uksi/1956/1769/schedule/n2/paragraph/1 (the official version)
Page: https://openlegislation.uk/coal-mines-precautions-against-inflammable-dust-order-1956/schedule-n2/paragraph-1
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.