Personal property cleaning is not quite the same thing as house cleaning. House cleaners clean surfaces and furniture. Personal property cleaners clean smaller items including books, jewelry, etc.
Most people never need to hire a personal property cleaner. They generally come in when there has been a fire, a flood or other situation that causes damage to the items inside a house, shop or office. They will work to clean and restore the items and return them to their place. Some things are cleaned with ultrasound and a cleaning solvent - this is a good technique for things like jewelry, watches, and firearms. Books and documents often require special attention and they need to be dried immediately. The same is often true of clothing.
Fire damage and water damage can also come together - when there is a fire and a sprinkler system or fireman's hose has put it out. These services can be expensive but are cheaper than replacing everything and can often save items that are irreplaceable. The cost, and the time it takes, depends on the number of items and their nature. For example, sometimes more expensive techniques might be used on irreplaceable documents. Of course, in some cases, some items may not be worth cleaning and restoring.
A good personal property cleaner will put together a plan for restoring your property and will help with removal, storage, and then returning the items to your home. It is the sort of service you hope never to need - but when you do, it is worth knowing where to start on finding a trustworthy cleaner who can help with everything that was damaged.
So, you would hire a personal property cleaner after a fire or flood. They might also be needed if you have a significant mold infestation. You may also be able to get the same service to clean and restore carpets and furniture.