law: Factories Act, 1948 
  36. Precautions against dangerous fumes,
  
  gases, etc. 
  
  (1) No person shall be required or allowed to enter any chamber,
  
  tank, vat, pit, pipe, flue or other confined space in any factory in which any
  
  gas, fume, vapor or dust is likely to be present to such an extent as to
  
  involve risk to persons being overcome thereby, unless it is provided with a
  
  manhole of adequate size or other effective means of egress.
  (2) No person shall be required or allowed to enter any confined
  
  space as is referred to in sub-section (1), until all practicable measures have
  
  been taken to remove any gas, fume, vapor or dust, which may be present so as
  
  to bring its level within the permissible limits and to prevent any ingress of
  
  such gas, fume, vapor or dust and unless- 
  (a) a certificate in writing has been given by
  
  a competent person, based on a test carried out by himself that the space is
  
  reasonably free from dangerous gas, fume, vapor or dust; or
  (b) such person is wearing suitable breathing
  
  apparatus and a belt securely attached to a rope the free end of which is held
  
  by a person outside the confined space.]