A metal shield in the form of a frustum of a cone, secured to the outer casing of the smokestack over the air casing to keep out the weather.
Isikhuselo sentsimbi esenziwe nge-"frustrum" yesibhumbulu, ngokuqinileyo kumphandle wesigqubuthelo sentsimbi ngaphezu komoya wesigqubuthelo, ukuqonda imo-zulu.