A ventilation apparatus includes a main body, an air entry and an air exit respectively arranged on two sides of the main body, a filter arranged behind the air entry, and a pressure sensor module located between the filter and the air exit, which senses pressure caused by air flowing inside the main body through the air entry and the filter. The pressure sensor module firstly senses pressure related data when the apparatus begins to start for initial data, and senses pressure related data continuously after the apparatus starts for working data, and transmits these data externally. An analysis monitor device computes a reference pressure offset value and a working pressure offset value according to the initial data and the working data, and compares the two pressure offset values for determining whether the filter needs to be replaced.