Radioactive material (Class 7) are articles or substances which, spontaneously and continuously, emit certain types of radiation (ionizing radiation) which can be harmful to health or affect other materials such as undeveloped photographic or X-ray films. These radiations cannot be detected by any of the human senses (sight, hearing, smell and touch), but can be identified and measured with appropriate instruments. It should be noted that appropriate instruments can detect and measure levels of radiation far below those which significantly affect health.