Farmers and ranchers bench-testing gasoline power saws or using combustible heaters for warming indoor maintenance areas risk exposure to lethal doses of carbon monoxide, warns William Steinke, a UC Davis Cooperative Extension farm safety specialist. "The National Safety Council estimates that between 500 and 1,000 people die annually as a result of carbon monoxide poisoning," Steinke says. "It's an odorless, colorless gas that can overpower a person before he or she is aware of what is happening." Symptoms of carbon monoxide poisoning include headaches, slurred speech, sleepiness and dizziness. Depending on the exposure level, the effects may be noticed within minutes or take several hours to appear. Removing a person from a gas-filled building does not always guarantee that he or she will recover. Instead, the individual should immediately be taken to a doctor. Many such accidental poisonings can be prevented by installing relatively inexpensive carbon monoxide detectors, similar to smoke detectors, in maintenance shop areas, Steinke suggests. .