9. Exemption.- The Government may, by order in writing and subject to such conditions and for such period, as may be specified therein, exempt from all or any of the requirements of these rules to -
(a) any building or other construction work, if the Government is satisfied that such building work is confined to such workers, where it is not convenient to take measures as provided in these rules; or
(b) any appliance, gear, equipment, vehicle or other device if the Government is satisfied that the requirement of such appliance, gear, equipment, vehicle or other device is not necessary for use or equally effective measures are taken in lieu thereof:
Provided that the Government shall not grant exemption under this rule unless it is satisfied that such exemption would not adversely affect the safety, health and welfare of building workers.