There are different types of venting systems for gas heaters. The most common type is called the “vented hood”. This is where a fan blows air out of the top of the heater and out through an exhaust vent. If you have this type of heater, it should be installed properly to allow for proper airflow. Another type of venting system is called the “hoodless”. This is where there is no fan or blower. It still needs to be installed correctly to prevent the risk of carbon monoxide poisoning.