34 people were made ill as a result of carbon monoxide poisoning at their Pennsylvania church, including some who had to be airlifted to a regional hospital. Authorities determined that the cause of the carbon monoxide poisoning was a blocked chimney for the church.
Winter poses a special increased risk of carbon monoxide poisoning for a few reasons. One is that there is an increased need for gas heat, and burning carbon based fuels such as gas or oil puts more carbon monoxide into the air. The other reason is that it is easy for things like chimneys, which are necessary to vent the carbon monoxide, to become covered with snow or ice, resulting in the carbon monoxide remaining in the building where it can rise to dangerously high levels.
Even though it is unpleasant to do in cold weather, periodic checks of chimneys and vents are an essential part of preventing carbon monoxide poisoning accidents.