Prolonged exposure to propane heaters can pose health risks if proper ventilation precautions are not taken. The combustion process of propane produces carbon monoxide, which is a colorless, odorless, and tasteless gas that can cause headaches, dizziness, nausea, and even death in high concentrations. Additionally, propane heaters consume oxygen from the surrounding air, which can lead to oxygen depletion, causing symptoms such as shortness of breath and fatigue. Therefore, it is crucial to ensure proper ventilation when using propane heaters indoors. Ventilation can be achieved by opening doors and windows or using a fan to circulate fresh air. It is also recommended to use a battery-operated carbon monoxide detector for added safety. By taking proper precautions and ventilation measures, the health risks associated with prolonged exposure to propane heaters can be mitigated, making them safe for indoor use.