in order to be responsive to fluctuations in ambient temperature decrease in ambient temperature cause the bellows to contract and the actuating arm 15 to be depressed thereby tending to open the damper when the temperature of the bimetallic strip rises the arms deflect in such a way by moving together to assist the closure of the damper at the commencement of an off peak period towards the end of the preceding on peak period e g in late evening if the room containing the heater was falling in temperature the actuating arm 15 would have opened the damper thus the damper would have been open at the commencement of the next off peak period which means that hot air will convect directly from the electrical heating elements through the internal air passage 8 and out through the ventilation apertures 12b in order to prevent wastage of heat and to avoid the danger of the heater casings 5 and 6 from becoming too hot the bimetallic strip is heated and as a result deflects to allow the damper to close in previous forms of storage heater a straight bimetallic strip has been attached to a damper actuating arm so as to act as a continuation of that arm.