Measure what matters
Write down floor area and ceiling height, along with whether doors usually stay open. Note where the appliance could sit and where you could refill it. A compact reservoir may be easier to carry, while a large reservoir can mean fewer refills.
Make a usable shortlist
Compare the method, controls, tank access and replacement consumables. Keep advertised coverage beside its stated test conditions. A large number on the box is not a prediction for every building.
Try the ownership routine
Before buying, read the cleaning section of the manual and check the regional warranty. Ask whether the tank fits your sink and whether replacement parts are sold locally.