law: Factories Act, 1948 
  37. Explosive or inflammable dust, gas, etc. 
  (1) Where in any factory any manufacturing process produces
  
  dust, gas, fume or vapor of such character and to such extent as to be likely
  
  to explode to ignition, all practicable measures shall be taken to prevent any
  
  such explosion by- 
  (a) effective enclosure of the plant or
  
  machinery used in the process;
  (b) removal or prevention of the accumulation
  
  of such dust, gas, fume or vapor;
  (c) exclusion or effective enclosure of all
  
  possible sources of ignition.
  (2) Where in any factory the plant or machinery used in a
  
  process such as is referred to in sub-section (1) is not so constructed as to
  
  withstand the probable pressure which such an explosion as aforesaid would
  
  produce, all practicable measures shall be taken to restrict the spread and
  
  effects of the explosion by the provisions in the plant or machinery of chokes,
  
  baffles, vents or other effective appliances.
  (3) Where any part of the plant or machinery in a factory
  
  contains any explosive or inflammable gas or vapor under pressure greater than
  
  atmospheric pressure, that part shall not be opened except in accordance with
  
  the following provisions, namely:
  (a) before the fastening of any joint of any
  
  pipe connected with the part or the fastening of the cover of any opening into
  
  the part is loosened, any flow of the gas or vapor into the part of any such
  
  pipe shall be effectively stopped by a stop-valve or other means;
  (b) before any such fastening as aforesaid is
  
  removed, all practicable measures shall be taken to reduce the pressure of the
  
  gas or vapor in the part or pipe to atmospheric pressure;
  (c) where any such fastening as aforesaid has
  
  been loosened or removed effective measures shall be taken to prevent any
  
  explosive or inflammable gas or vapor from entering the part of pipe until the
  
  fastening has been secured, or, as the case may be, securely replaced:
  PROVIDED  that the provisions of this sub-section shall
  
  not apply in the case of plant or machinery installed in the open air.
  (4) No plant, tank or vessel which contains or has contained any
  
  explosive or inflammable substance shall be subjected in any factory to any
  
  welding, brazing, soldering or cutting operation which involves the application
  
  of heat unless adequate measures have first been taken to remove such substance
  
  and any fumes arising there from or to render such substance and fumes
  
  non-explosive or non-inflammable, and no such substance shall be allowed to
  
  enter such plant, tank or vessel after any such operation until the metal has
  
  cooled sufficiently to prevent any risk of igniting the substance.
  (5) The State Government may by rules exempt, subject to such
  
  conditions as may be prescribed any factory or class or description of
  
  factories from compliance with all or any of the provisions of this section.