Propane heaters can be used as a primary heat source for a home, but it is crucial to follow specific safety precautions. When using propane heaters for primary use, it is essential to only use indoor-rated heaters as they are designed to emit lower levels of carbon monoxide gas. Ventilation is necessary even with indoor-rated heaters to prevent the buildup of CO gas. It is recommended to use a battery-operated carbon monoxide detector for added safety. It is also crucial to keep the heater away from potential fire hazards. Oxygen depletion is a separate danger, and heaters with ODS shut off if oxygen levels go below 18%. However, these heaters won't work above 4,000 feet. Proper precautions and safety features make propane heaters safe for indoor emergencies, including primary heating, but it is essential to follow all safety guidelines to avoid any potential risks.