Ductless fume hoods are fume cabinet that does not require any external ventilation. Instead, they use filters to capture solvent fumes from circulating air, which is then vented into the room. Ductless fume cabinets can maintain the same air flow as a standard vented fume hood, but are easier to install since they do not require ventilation ducts. Sensors inside the ductless fume cabinet monitor gases, and an alarm sounds if the filter becomes overwhelmed and fumes escape. A ductless fume hood is best used for applications that require small volumes of solvents, since the filters can become saturated quickly with large volumes. Therefore, reagents should never be stored inside a ductless fume hood. When used as directed by the manufacturer, a ductless fume cabinet can be a welcome addition to a laboratory, especially when space is at a premium and a full vented fume hood will not fit.