Which type of appliance is suitable for installation in a confined space such as a bathroom?

The direct vent heater is suitable for installation in confined spaces like bathrooms because it is designed to draw air from the outside for combustion and exhaust fumes directly outside, ensuring that the indoor air quality is not compromised. This arrangement is particularly important in small or poorly ventilated areas where the risk of carbon monoxide accumulation or depletion of oxygen is higher.

Direct vent heaters maintain efficiency and safety in a confined space by utilizing a sealed combustion system in which the burner is isolated from the indoor air. This makes them ideal for installation in locations that may not have sufficient ventilation, such as bathrooms, as they do not require indoor air for operation.

The other options present certain challenges. Unvented gas heaters can pose safety risks in confined spaces due to the potential release of combustion byproducts into the indoor air. Wall-mounted electric heaters do not use gas, hence are safe but may not be designated for areas requiring gas appliances. Gravity vent gas heaters rely on natural convection for venting, which may not be effective in a confined space, potentially leading to dangerous conditions. Thus, the direct vent heater is the most appropriate choice for safe and efficient operation in such environments.