Many chemicals are hazardous. Numerous OSHA standards regulate and limit exposure to individual hazardous chemicals. Chemical hazards include physical hazards, such as fire, explosion, or reactivity, and can often also present health hazards. In other words, exposure may be seriously harmful to a worker's health. Physical hazards are easy to identify with objective measures like flash point and boiling point. But health hazards may offer only a variety of symptoms, or sometimes no symptoms at all.