This part of ISO 7240 specifies requirements, test methods and performance criteria for smoke-detection equipment for ducts (s.d.e.d.) for use in fire-detection and fire alarm systems installed in buildings; see ISO 7240-1. The s.d.e.d. samples the air from a duct and detects smoke in the sample. NOTE 1 A common method of operation is to use differential pressure arising from airflow in the duct. The s.d.e.d. can use smoke detectors complying with ISO 7240-7 or other detectors complying with tests specified in this part of ISO 7240. A common application for s.d.e.d. is to detect visible smoke, for which detectors using scattered light or transmitted light can be more suitable. However, requirements for detectors using ionization are also included in this part of ISO 7240 for use in applications where detection of less visible fire aerosols is desired. For the testing of other types of smoke detectors or smoke detectors working on different principles, this part of ISO 7240 can be used for guidance. Smoke detectors with special characteristics, developed for specific risks, are not covered. NOTE 2 Certain types of detectors contain radioactive materials. The national requirements for radiation protection differ from country to country and are not specified in this part of ISO 7240.