To Whom PF Is Applicable?

Dear friends,
My company was started with 15 employees from 2008 to April 2010,
The count is increased to 30 employees in May 2010.
I want to know whether PF will be applicable from 2008 onwards or May 2010 onwards.
Please give me solution regarding this.

when our propritor firm ( Trading Company) applicable pf number

EPF IS APPLICABLE TO ALL PVT.ESTTS.HAVING 20 OR ABOVE WORKERS...
AND CENTRALGOVT.NOTIFIED ESTTS .20 OR EVEN BELOWWORKERS.
3.contract labour eligible.
4,Temporary employees and trainees and Apprentices not eligible
5. Any new estts EPF applicability starts only after 3years ...
6.mnimum salary for eligibility to EPF is 5000Rs.per month.
7A company started 3yrs ago
...an employee joined newly...
he gets eligibility for EPFcoverage
from the date of joining..
EPF pension scheme applicability of employee Up to 60 yrs .only

Hi to all I went through the discussion my doubt is in my company we are 15 can PF be applicable.