Light Cleaning (Up to 3): They have low pressure and are more suitable for disinfection than for stain removal.
For the whole house (3.1 - 3.9): They have moderate steam pressure and besides their sterilization property, they can clean smooth surfaces (sinks, floors, etc.).
For stubborn dirt (4 and above): They have high steam pressure and excellent performance in cleaning hard surfaces and stubborn stains (grease and residues on grills, oven racks, etc.).