Whilst the preference would be to incorporate fully ventilated fume cupboards within a design/proposal, with foul air being vented to atmosphere, stand-alone recirculating fume cupboards are available. The advantage of a recirculating fume cupboard is that less consideration needs to be given to providing air replacement equipment to help provide a balanced laboratory environment. The safe performance of a recirculating fume cabinet relies on specifying the correct type of filters at design stage. Without specific information relating to the hazards that may be emitted from an experiment, the function of any recirculating cabinet will be compromised. In compromising the performance of any filters will create a health hazard to any laboratory user. When specifying a recirculating fume cupboard iab will present you with a demanding series of questions and documents to fill in. This is necessary so that engineers can design and specify the correct filters. Filters need to be replaced when indicated by the fume cupboard monitoring system.