We think of our homes as our refuge, our places of fun, relaxation and safety after long days at work or school.

But sometimes something dangerous can lurk at home that goes unseen and undetected – a gas that can cause serious illness or even death.

When someone inhales carbon monoxide – often called the “silent killer” -- the carbon monoxide displaces the oxygen in the victim’s blood, according to the Geneva Fire Department website. Because no one can smell, see or taste it, people have no idea they are being poisoned until it is too late.

Every year, 20,000 to 30,000 people in the United States are sickened by accidental carbon monoxide poisoning and approximately 500 people die, many in their own home because carbon monoxide cannot be detected by humans without the help of a detector.

That’s why safety experts consider it so important that families be prepared by outfitting their home with alarms near every bedroom. In Illinois, state law requires that every “dwelling unit” be equipped with at least one approved carbon monoxide alarm within 15 feet of every room used for sleeping purposes.

With the right equipment and knowledge, residents can know they are doing all they can go keep their home safe and stop a potential horrific tragedy.

Carbon monoxide is a deadly gas produced by incomplete burning of any fuel and is a common by-product of vehicle exhaust, improperly vented fireplaces, grills, wood stoves and appliances that run on fuel-burning appliances such as gas furnaces, ovens, stove burners, and portable heaters.

So what can you do to make sure you are not a victim? Place a detector on every floor. Big box stores sell plug-in detectors that use an outlet with a battery back-up. There are also combination smoke and carbon monoxide detectors that you can install to cover both dangers.

Home appliances should always be checked to ensure that they are in good working order and properly ventilated by a qualified professional. All combustible appliances produce some level of carbon monoxide. However, if the appliances are in good condition, meant for indoor use, have adequate venting, and are maintained regularly, there are usually no safety issues.

What to do if your carbon monoxide detector starts beeping? First things first, go outside to fresh air. If you experience any symptoms of carbon monoxide poisoning, it is crucial that you leave the premises immediately, leaving windows and doors open if possible. Call 9-1-1 only once you are out of the vicinity as the gas could cause unconsciousness before you can call for help. The fire department will send personnel out to your home with equipment to test the levels and where in your home they are elevated.

The symptoms of carbon monoxide poisoning may not be obvious, if even felt at all. Some people say that they thought they were coming down with the flu. However, if more than one person is experiencing the same thing or symptoms occur when you are in one part of the home but go away when you move elsewhere, this could be carbon monoxide poisoning.

Symptoms include: headache, dizziness, nausea, weakness, loss of muscle control, tightness in the chest, difficulty seeing, shortness of breath, sleepiness and skin redness.

This month, do a quick inventory of your carbon monoxide alarms and make sure they have fresh batteries and are placed in the appropriate places.