If you are even remotely concerned about carbon monoxide in your home then the smartest thing you can do is to go and buy a carbon monoxide detector from a big box store and plug it in any electrical outlet, one on each level of your home. These devices cost a little more than a cheap smoke detector and are well worth the expense for any home because just like smoke detectors, they save lives. most reputable HVAC contractors have carbon monoxide meters and almost all gas companies have them as well, they can come to your home and measure the carbon monoxide levels in your home. Having said that you should also have your furnace inspected by a qualified HVAC contractor if you even suspect your furnace is leaking and all manufacturers recommend that the furnace be inspected and serviced annually. 

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