Can't puff the air filter!!Otherwise the symmetrical clearance between compact
filtering fiber will be destroyed.The filtering function will be lost.It will
bring bigger particle can go through filtering paper successfully.
In the filtering industry,there is one speaking that dust can filter dust!The
new air filter's filtering function is even worse than old air filter who is
used for some times.
The standard of changing air filter is not the surface of the air filter is
dirty or not. It is the air press gets to 25cm water column.
So,The way of reserving air filter is not puff the air filter! The best way is
to change the air filter after driving 15,000km to 20,000km!