of crude oil based fuels to consumers in the United Kingdom or persons carrying on  business in the United Kingdom; and  where they have travelled to the United Kingdom in the course of their work.  (2) For the purposes of sub-paragraph (1)—  29. —(1) A worker required to undertake or commence within the period during which they  would, but for this paragraph, have had to self-isolate in accordance with regulation 9—  where they have travelled to the United Kingdom in the course of their work.  (2) For the purposes of sub-paragraph (1)—  30.  A postal operator, as defined in section 27(3) of the Postal Services Act 2011( d ), where they  have travelled to the United Kingdom in the course of their work.  31.  A worker with specialist technical skills, where those specialist technical skills are required  for essential or emergency works or services (including commissioning, maintenance, and repairs  and safety checks) to ensure the continued production, supply, movement, manufacture, storage or  preservation of goods, where they have travelled to the United Kingdom in the course of their  work or otherwise to commence or resume their work.  32.  A worker with specialist technical skills, where those specialist technical skills are required  for  essential  or  emergency  works  (including  construction,  commissioning,  installation,  maintenance, repairs and safety checks) or to fulfil contractual obligations or warranty  specifications in, or in connection with, waste management facilities used for the management,  sorting, treatment, recovery, or disposal of waste (including energy from waste), where they have  travelled to the United Kingdom in the course of their work.  ( a ) 1998 c. 17. Section 44 was amended by paragraph 11 of Schedule 1 to the Energy Act 2008 (c. 32).  ( b ) Section 9H was substituted by section 74(2) of the Energy Act 2016 (c. 20).  ( c )  Section 45A was inserted by section 75(1) of the Energy Act 2008. There are amendments to section 45A(10) but none is  relevant.  ( d ) 2011 c. 5.  43 (b) the activities are required to ensure continued safe operation of the facility,  (a) a facility has a capacity in excess of 20,000 tonnes at any time if it was used in the  previous calendar year for the purposes of downstream oil sector activities in relation to  more than that number of tonnes of oil;  (b) “specified activities” are—  (i) storing oil,  (ii) handling oil,  (iii) the carriage of oil by sea or inland water,  (iv) conveying oil by pipes,  (v) refining or otherwise processing oil.  (a) activities on or in relation to an offshore installation;  (b) activities on or in relation to upstream petroleum infrastructure;  (c) critical safety work on an offshore installation or well being decommissioned or  preserved pending demolition or reuse; or  (d) activities for the provision of workers, goods, materials or equipment or other essential  services required to support the safe operation of the activities referred to in paragraphs  (a) to (c),  (a) “offshore installation” has the meaning given in section 44 of the Petroleum Act 1998( a );  (b) “upstream petroleum infrastructure” has the meaning given in section 9H of the  Petroleum Act 1998( b );  (c) “well” has the meaning given in section 45A(10) of the Petroleum Act 1998( c ). 