[veesubotee]

hello, please tell me how to measure the cfm (air flow in duct system) and whats the meaning of cfm. thanx

CFM = cubic feet per minute.

There are types of instruments for measuring airflow, perhaps a little pricey if you're not in the trade. There are also some formulas where, knowing some values, one can derive CFM.

If you describe your concerns or problems, perhaps some PROs will be able to give you some advice.