Can any one guide us what are the various parameters we have to look for HVAC Validation and what are their limits.
A good start would be to get the new Easy to understand guideline for HVAC validation from Ask About Validation
http://www.askaboutvalidation.com/validation-products/product.php?id_product=21
, and then to put more details to your questions, as it is a bit too unspecified to answer directly.
Understanding your needs is the starting point, for deciding what paramateras are relevant at your facility, and then to set limits for these, as step two.
/Helena
ISPE Good Practice Guide: Heating, Ventilation, and Air Conditioning (HVAC) is a very good resource to help understand HVAC