By essential service, I only meant those services which cannot be suspended. For example, in a boiler and work related to it, there should be some workers engaged round the clock. Similarly, urgent repair work that has to be attended to, without which the factory might remain closed on Monday or the following day, is also considered essential work.
Regarding contract labor, I have a different opinion because contract laborers are engaged in work of a non-perennial nature which has no direct connection with the routine work of the company. Therefore, there is hardly any urgency to engage them on national holidays. It is advisable to avoid engaging them on holidays.
Regards,
Madhu.T.K