When choosing the right portable air conditioner for your needs, you will likely notice that there are two types of hose configurations to choose from: a single hose or dual hose. Single-Hosed Portable Air Conditioners The most basic is the single-hose design, which uses a compressor to power the cooling system and remove heat from the room’s air. Single-hose units pull air from within the room and expel warmed air and moisture outside. This can create “negative air pressure” because air is constantly being pushed out of the room, and as a result, the air in the room has to be replaced. Subsequently; warm air seeps in around doorways, and through structural cracks and holes, attempting to replace the “missing” air. The unit is then forced to work much harder to keep the room cool. Though single-hose units are effective and provide ample cooling for most spaces, their design is much simpler and less efficient than dual-hose portable air conditioners. Recommended Single Hose: EdgeStar AP12000S Dual-Hosed Portable Air Conditioners The dual-hose design utilizes two separate exhaust hoses, one of which will function as air exhaust hose and one that will draw air in from the outside. The air that is taken in from the room is cooled inside the unit and then expelled back into the room. The process of cooling this air generates heat inside the unit, in order to cool the unit, the second hose intakes air from the outside which is used to cool the unit’s compressor and condenser coils. Recommended Dual Hose: EdgeStar AP14001HS The advantages of the dual house design are in its ability to cool an area more efficiently and quickly, while requiring less work for your portable air conditioner. An additional consideration in your choice of hose design is the lifespan of the unit’s filter. In a single hose design more unfiltered air is entering the unit and therefore shortens the length at which your unit’s filter will remove allergens from the expelled air. Though single hose units may tend to be slightly less expensive, the investment in the extra hose is definitely worth the extra cost.