Gas flaps (gastight valves) are fitted as necessary in the trunking to allow uncontaminated air to be re-circulated in the citadels.
Amadlebe eyesi (izivalo ezingangeni gesi) zifakelwe ngekufane-lekileyo emibhobhweni ukuvumela umeya ococekileyo abenokujikeleza ekhusini.