I do not know much about Karnataka Factory Rules but there are Model rules framed by DGFASLI, Mumbai which are then adopted with some changes here & there by State Legislative Assemblies to form State Rules. According to the Sec 87 of the Act, State Govt are empowered to declare any operation being carried out in Facotry as 'Dangerous', it may make rules applicable. Under Sec.85, State Govt are empowered to make the Act applicable to certain premises. So, normally, as general principle, State Govts lower the number of workers for applicability of the Act in case of Hazardous Operations. One may find the list of Haz.Operations declared by State Govt in the State rules under the chpater "Special Provisions". In Gujarat Chemical works, areas in factory with high oise, ( Higher than 90 dB), Welding/Cutting,Foundry,Glass industry,Ginding or glazing of metals, Places where Mercury, lead, Asbestos, Silica, Chromium ect are handled and workers are exposed to them etc.In Gujarat The Act is applicable to the units employing 5 or more inHaz. OPerations but in soem Haz. Operations, even if one worker is employed, Factory Act /Rules are applicable. Govt of Gujarat publishe dnotification in Nov.2008 and according to this notification, units where Asbestos is handled, Act will be applicable even if 1 worker is employed. Website of Karnataka Govt should have this information