Carbon monoxide is tasteless, odorless and dangerous to humans, animals, and plants. Fortunately, there are many visible signs indicating the presence of carbon monoxide.

* Black soot on or around air registers, flues, burners or access openings to appliances.
* Condensation of moisture on inside windows (humidifiers & vaporizers can also cause condensation).
* Dead or dying houseplants and animals
* Abnormal flame characteristics, such as a yellow gas flame instead of blue, flame rolling out of the front of an appliance, or flame lifting off the burner.