I have to hoover my home fairly frequently due to haveing a dog (Roxy!) but I have found that over time, although the suction on my machine remains strong, it starts to smell a bit.
I have a Dyson and take time to clean the container that collects the dust and dirt and use a brush to clean away debris from any visible parts but sometimes that isn’t enough to get rid of the smell.
Unfortunately, the way all vacuums are designed, air is sucked in along with any dirt, and air is blown out. It is this air that is emitted that sometimes can smell a bit musty.
When I have performed a clean of the machine I like to add a few drops of essential oil* (my favourites are lemon, lime or orange) to a cotton ball or tissue and place that into the container before replacing on the machine. Another thing I like to do is to remove and clean the filters, thoroughly dry them and add a little bit of scent to the filter. I try to steer clear of adding oils to the filter as they can capture dust and block up the filter really quickly, instead I like to spritz on some room spray or a body spray (my favourite scents for this is Charlie Sexy – a vanilla orchid scent) which leave the room smelling lovely with a hint of scent rather than being too overpowering.
*If you have pets, please be careful when using any essential oil or any product that contains essential oils as some oils can be toxic or even fatal to pets. Please do your research before using any essential oils.