Abstract: This invention relates to temporary closures for a room vent and is particularly although not exclusively applicable to temporary closures for room vents to enable a room to be sterilised by circulating sterilant vapour without allowing vapour to enter the vent or gas to enter the room from the vent during the sterilising operation. The temporary closure comprises a hood to extend over the vent having a peripheral seal for engaging a surface around the vent and a telescopically extendable strut on which the hood is mounted to engage a fixed surface disposed opposite the vent to hold the hood in place over the vent.