Lee, (Marquette, MI)
Lee, although the howling noise could be caused by vibration, resonance, or a foreign object inside your furnace, the fact that the CO or LP detector is going off and you can smell “gas” is a much more telltale and dangerous sign. This is an indication of incomplete combustion. The howling you are hearing could be the sound of the burner fuel simply not mixing properly with the air, thus causing faulty combustion. In some furnaces, a primary air adjustment can eliminate the howling. Without a brand or model number though, it is impossible to discern if yours is the adjustable type. I’m more concerned about the odor that is emitted. The most common by-products of incomplete combustion are aldehydes (poisonous gasses) and CO, both of which are extremely toxic. Like a howling noise, the incomplete combustion could be caused by the same improper mixture of air and LP in the combustion chamber. A loose or damaged combustion wheel could also contribute to this. It could also be caused by a partial airflow blockage or an incorrectly adjusted or damaged burner component. Whichever the case, it is imperative you have the furnace serviced as soon as possible by a qualified RV service center. They are trained and certified to troubleshoot, repair and service the LP appliances. All LP appliances should be cleaned and serviced at least once a year. There is a set of specific maintenance steps to be performed on each appliance.