Ventless gas heaters are heating devices that operate without the need for a chimney or venting system. They burn natural gas or propane to produce heat, which is then released directly into the room. This design allows for easy installation in various spaces, making them a popular choice for homes and small areas. These heaters are typically equipped with safety features, such as oxygen depletion sensors, to ensure safe operation. While they can be efficient and cost-effective, it's important to use them in well-ventilated areas to prevent the buildup of carbon monoxide and maintain indoor air quality.