Section 24-173. Use of solid fuel

(a) Except as provided in subdivision (c)
  of this section, no person shall cause or permit the use of  solid  fuel
  in fuel burning equipment to provide heat or hot water for any structure
  or any part thereof, other than the generation of steam for off-premises
  sale.
    (b)  No  person  shall  cause  or permit the use of solid fuel in fuel
  burning equipment for any purpose  whatsoever,  unless  he  or  she  has
  complied  with subdivision (c) of this section. No person shall cause or
  permit the use of bituminous coal in fuel burning equipment,  for  which
  an  operating  certificate  or  certificate  of registration is required
  pursuant to this chapter for any purpose whatsoever.
    (c) Solid fuel, unless otherwise prohibited by this  section,  may  be
  used for fueling boilers used for on-site space heating, provided that:
    (1) No expansion of capacity of the boiler shall be made over capacity
  existing on May twentieth, nineteen hundred sixty-eight; and
    (2) Only anthracite coal is used; or
    (3) The solid fuel shall meet the following criteria:
    (a) Volatile content shall not exceed thirty-two percent by weight.
    (b) Fixed carbon shall not be lower than sixty-six percent by weight.
    (c) Ash shall not exceed four percent by weight.
    (d) Sulfur shall not exceed 0.7 percent by weight.
    (e)  Heating  value  shall  not  be  less than fourteen thousand seven
  hundred fifty Btu/lb.
    All the above criteria shall be measured on a dry basis.