Most homes in the area use forced-air furnaces to stay warm. They are effective and cost-efficient means of heating the household: using gas-fed burners to heat the air, which can then be blown into your home with a fan.
The heat exchanger plays a vital role in that process, and while it’s intended to last for many years, older heat exchangers can develop cracks and fractures, which are a serious problem. If yours develops such issues, you need to call a heating repair service immediately. It’s all the more important to keep a close eye on your system now, since you’re likely using your furnace more often in January than you are any other time of the year.