An apparatus applicable to a storage container is provided and includes a filtering cartridge, a gas supply device and a particle counter. The filtering cartridge is configured to be disposed on the storage container. The filtering cartridge includes a flexible housing and a filter. The flexible housing has a first portion and a second portion opposite to the first portion. The flexible housing includes a gas inlet, a first gas outlet and a second gas outlet. The gas inlet is disposed on the first portion. The first gas outlet is disposed on the first portion. The second gas outlet is disposed on the second portion and connected to the storage container. The filter is disposed over the second gas outlet. The gas supply device is connected to the gas inlet, thereby purging gas into the flexible housing. The particle counter is connected to the first gas outlet.