context: Ovens and grills help us stay fed. Heaters keep us warm. Cars take us where we want to go. And whenever we turn on devices that run on natural gas, charcoal, gasoline, wood, or other fuels, we have to use them the right way. Carbon monoxide, produced any time a fossil fuel burns, is a gas you can't see or smell. Ovens, heaters and other devices put out little of it when they're working properly. But if they're out of order, or if people use them in the wrong places, the fumes can build up. This can be life-threatening. There are things you can do to stay safe. And battery-operated detectors that are easy to find at stores can warn us of trouble. Someone who is asleep can die from carbon monoxide poisoning without ever waking up. That's all the more reason to make sure your home is safe. When you buy appliances that burn fuel, look for the seal of a testing agency such as UL. In your home, any equipment should be installed with vents running outdoors. Here are more tips: Maintenance: Have a qualified technician inspect your heating system, water heater and any other fuel-burning appliances every year. If you have a fireplace, the chimney needs a going-over. Emergency generators: Don't use them in your garage or basement. Put them outside the house at least 20 feet from windows or doors. Charcoal grills and portable camp stoves: Use them only outdoors. Space heaters: Use them only when someone is awake to keep an eye on them; make sure there is some airflow in and out of the room. Don't try to use a gas oven for heat. Vehicles: Have your car or truck's exhaust system checked each year. If your garage is attached to your home, don't leave a vehicle running there. Even with the garage door open, the fumes can seep inside the house. If your vehicle has a tailgate, be sure to open windows anytime you drive with the tailgate down. If you don't, carbon monoxide can be sucked into the vehicle. By keeping your eyes open, you may spot evidence that appliances are out of whack or something else is wrong. A few danger signals: Soot falling from fireplaces or appliances. Rust or water streaks on vents. Loose or disconnected vent pipes. Moisture inside windows. Cracked or crumbling masonry on a chimney. If you see any of these, have a trained technician check them out and fix whatever needs it. These detectors are available at hardware stores and other retailers, and your home should have one or more. Buy alarms that are certified by a testing laboratory. Follow the instructions about installation. Here are a few other guidelines: Detectors should go on each level of the home and outside each sleeping area. Test the alarms once a month. Some alarms also give off audible signals on their own if the battery runs low or they break down. If you have multiple alarms, connect them all together. That way, if one of them detects trouble, they all go off. Before there's any trouble, ask your fire department for the number to call if the alarm goes off. If you have a boat or motor home, detectors are also available for there. If you inhale too much carbon monoxide, it builds up in your bloodstream, where it takes the place of the oxygen that belongs there. When your heart, brain, or other vital organs are deprived of that oxygen, you're in trouble. If the dangerous gas is getting into your system, you might: Feel short of breath Get dizzy Become nauseous Get a headache Feel confused Carbon monoxide is especially dangerous for infants, pregnant women, and people with ailments such as emphysema (which damages the air sacs in your lungs), asthma or heart disease. Smaller amounts of the fumes can hurt them. If you think carbon monoxide is affecting you or your alarm sounds, move to fresh air -- either next to a window or open door, or outside. Make sure that everyone else in the house is also in the clear. If anyone has symptoms of carbon monoxide poisoning, get emergency help. More than 20,000 Americans go to emergency rooms each year because of carbon monoxide poisoning, and more than 400 people die. Don't go back into the house until it's safe. Your fire department can help you figure that out.