Abstract: An improved ductless fume hood with an improved system for monitoring filter life and an improved design for extending filter life is disclosed. The improved system for monitoring filter life consists of sensors upstream and downstream of the hood filter. A comparison of the readout of the upstream and downstream sensors allows for calculation of the efficiency of the filter. An alarm may then be triggered when the filter efficiency falls below a pre-determined value. The improved design of the ductless hood is the inclusion of a novel diffuser located upstream of the hood filter that allows for even filter loading. Even filter loading allows more of the volume of the filter to be used, extending filter life.