A Cold-Light Stick or chemstick is a sealed plastic tube, usually 10cm long. The interior contains two chemicals separated by a plastic or thin glass membrane. When bent and shaken (mixing the chemicals) it starts a bioluminescence chemical reaction, producing a soft glow. The light cannot be turned off once started. Once the chemical reaction has run its course, the tube is discarded.
Cold-Light Sticks are usually supplied in multi-packs.
At TL-7 glow sticks are often quite crude and are more suitable as children's toys than proper emergency devices. At TL–8 the glow is a soft green color and persists for 30 minutes. At TL–9 the chemicals can produce any color, including white and infrared. The glow persists for 5 hours. At TL–10 the chemical reaction lasts for 24 hours.