During a fire the ceiling cavity can allow fire or smoke to spread throughout a building to inhibit fire entering the cavity via the ceiling loudspeaker it can be fitted with an lbc 308001 steel fire dome this is mounted on the loudspeaker assembly using four self tapping screws supplied with the fire dome the fire dome has knockout holes for two grommets supplied and two cable glands pg 13 this fire dome can only be used with the ceiling speakers lbc 308741 lbc 309001 lbc 30903