Before enforcing a Declaration, it's important you should arrange COVID PCR test of all employees so that infection, if any, carried by a or a few should not spread to others & inside the unit. If any one found positive the fact should be informed to the state appointed Nodal officials for necessary action and proper quarantine. Mere declaration will not give a desired result.
It's also important to sanitise entire unit with prescribed chemicals & should be repeated as frequently as required as per guidelines. Enforce on all entering your units with proper PPE, observe social distancing, hand sanitiser, gloves etc.