Formaldehyde has been used in many different applications. It can be found in plywood and particle board. Some fabrics have formaldehyde in them, as well as, some glues among other things. While minimal exposure to this chemical might not have a harmful effect on you, you should exercise care and it might be wise to remove some sources of it.
Exposure to formaldehyde can cause a range of ill effects, ranging from watery eyes, fatigue and allergic reaction to something as serious as throat cancer. This is why it makes sense to limit your exposure.
While it might be difficult to find out whether you have furniture or something similar that releases formaldehyde into the air in your home, sometimes you might get a whiff of its pungent odor. You should also be able to find out more information about the materials used in the production of your furniture from the manufacturer, which might help you figure out whether or not you are at risk.