These agents are all crystalline solids, which are released as smoke when heated. Smoke produced by DM is a light or canary yellow, while DA and DC produce a white smoke. These agents are highly effective in low concentrations, which may not be detectable during exposure. Symptoms produced include a feeling of pain and sense of fullness in the nose and sinuses, accompanied by a severe headache, intense burning in the throat, and tightness and pain in the chest.