Start with the problem you want solved
Start with the concern you are trying to address: visible dust, odors, humidity, ventilation or discomfort.
White City: planning the visit
White City has its own municipal government. If a replacement furnace must fit an existing utility closet, bring the opening dimensions and photographs showing the surrounding space. Ask how removal, ventilation connections and service access will be handled. An installation drawing and a discussion with the appropriate permitting authority are more useful than choosing a unit solely from its advertised rating.