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FLORISSANT, MO (KTVI)– A couple dies in Florissant and police say the changing weather patterns contributed it. Now Florissant firefighters are on mission to prevent more deaths.

The husband and wife were found in their home Sunday night by a neighbor. Police say the cause of death was carbon monoxide poisoning.

Firefighters went door to door in their neighborhood Wednesday warning residents about this silent killer.

Like all of the other homes in the neighborhood, the couple’s brick home was built in the 50’s on a concrete slab with radiant heating. A cooling system was added years later with a separate thermostat.

Police say with the hot temperatures over the weekend the air conditioning was turned on and at night when cooler weather moved in the heating thermostat also kicked on.

The couple’s names have not been released yet.

If you have separate thermostats firefighters urge you to get it converted to one thermostat or always make sure one is turned off. They also advise everyone to buy a carbon monoxide detector and install in the bedroom so you’ll hear it while you’re sleeping.