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Combustion Air
To guarantee that sufficient oxygen (fresh air) is available for your heater, good ventilation is
essential. It is necessary to replace the air inside your boat at the same rate that the heater is
removing it. The higher the heater’s burning rate, the more air the heater will require. If the air
flow is blocked (the ‘draft’) or restricted, the heater will burn inefficiently, create soot or even
blow out.
A permanently open fresh air inlet should be installed. This inlet must be at least 3" in
diameter. Ducting fresh air to the heater is most satisfactory. It is important to create and
maintain a positive pressure inside the boat. High winds can draw air from the boat and thus
create a negative pressure. This condition can result in down drafts. Ensure that when you do
have widows open that they do not create a suction effect in the cabin due to the window’s
position and the wind direction. In a similar way, it is possible for the air intake on your
engine to suck the air out of a cabin if it is not properly vented.
