Devices and methods for using visible light of wavelengths between 760 to 610 nanometers, here termed Anti-Carcinogenic or CancerSafe or CancerGuard light. When irradiated upon animals during their customary sleeping hours, or when they are sleepy, or have been sleeping, Anti-Carcinogenic night light does not disrupt the hormonal secretions of the pineal gland. Conventional light, associated with pollution of the sky and urban areas, disrupts hormonal secretions, and much evidence points to hormonal secretion disruptions as a cause of cancer. The novel Night Lights can illuminate areas adjacent bedrooms, dormitories, and in vehicles, buses, aircraft, where passengers customarily sleep, and in refrigerators, and on illuminated clocks and watches. These Night Lights can have back-up power supply and employ motion sensors and photoelectric switches to switch on Anti-Carcinogenic (non-carcinogenic) illumination when needed for safe movement in otherwise darkened areas, and can detect power failures, noises indicative of violence, such as panics, school shootings, cries for help in medical emergencies, or assaults, and also detect dangerous, toxic, or explosive substances, including particulates, bacteria, viruses, thereupon they communicate alarms by sound, optical cable, laser, or radio frequency. Also covered are devices converting conventional carcinogenic night lights to Anti-Carcinogenic ones, and translucent window drapes and light traps to convert other light sources to Anti-Carcinogenic light.