Envirovent Silent 100 100mm 4" Axial Fan with TimerOverview The Silent 100 from Envirovent is high power silent running bathroom extractor fan. Suitable for wall and ceiling mounting it has been designed to prevent condensation and remove odours from bathrooms and toilets. The Silent range features motors mounted on silent elastic blocks ensuring exceptional performance while quietly whispering away in the background. The SIL100T features an adjustable overrun timer which can be set from 1 30 minutes.