CDC reminds us of some of the basic ways to prevent this from happening.

How can I prevent CO poisoning from my home appliances?

• Have your heating system, water heater and any other gas, oil, or coal burning appliances serviced by a qualified technician every year.
• Do not use portable flameless chemical heaters (catalytic) indoors. Although these heaters don’t have a flame, they burn gas and can cause CO to build up inside your home, cabin, or camper.
• If you smell an odor from your gas refrigerator’s cooling unit have an expert service it. An odor from the cooling unit of your gas refrigerator can mean you have a defect in the cooling unit. It could also be giving off CO.
• When purchasing gas equipment, buy only equipment carrying the seal of a national testing agency, such as the American Gas Association or Underwriters’ Laboratories.
• Install a battery-operated CO detector in your home and check or replace the battery when you change the time on your clocks each spring and fall.http://www.cdc.gov/co/faqs.htm

In Depth CO Poisoning Info From the CDC