How do I know if my diffuser is still working or if there is still perfume?

When the diffuser is running, it generates a slight mist at its output.
To see it, just look at this output on a black background (or place a black paper behind the stream) to check if the mist is present.
If the mist is present and you no longer smell the perfume it is because you have probably become accustomed to it.
If there is no mist when the program is running, either the refill cartridge is empty or the diffuser needs to be replaced.
In any case contact us to help you at best.