warm-air circulation. The flame burns in a closed satisfactory than the unvented type because there is combustion chamber, and the heater vent carries away less danger of carbon monoxide poisoning. A panel the gases (fig. 4-5). The flow of heat is maintained by a unit is one type of vented unit (fig. 4-6). It may be motor-driven fan and is controlled by vanes, fins, recessed or surface-mounted in either an interior or louvers, or diffusers. This type of unit is more exterior wall with a vent properly insulated and run up

Figure 4-5. - Rear view of a vented gas-fired space heater.

Figure 4-6. - Gas-fired panel space heaters.