A vented Martin propane heater can be used as a primary heat source. Vent-free, hydrocarbon-fueled heaters should not be used as a primary heat source in enclosed spaces because of the accumulation of combustion byproducts in the air.
Propane combustion consumes oxygen and releases carbon monoxide, nitrogen dioxide, unburned hydrocarbons, carbon dioxide and water vapor. Well-insulated, enclosed spaces trap the released gases and particulates and inhibit the replenishment of oxygen levels. Carbon monoxide can be fatal at high levels and causes long-term health issues at sustained, low levels. Exposure to nitrogen dioxide can affect the immune system and increase the incidence of respiratory illness.