Identify the particles, odours, or general air quality concerns the unit is expected to address, then examine the stated filtration stages. Different filters may serve different roles, such as capturing larger dust, finer airborne particles, or certain odours. Do not assume every purifier handles every contaminant in the same way. Consider replacement intervals, filter availability, and whether several filters must be changed separately. Operating cost can become significant in areas where the unit runs for long periods. Also consider whether an indicator shows when service is due and whether staff can replace filters without exposing the room to collected dust. The purifier should be selected for its documented filtration capability, not broad health claims that the manufacturer does not support.