In what case can living space air be used for combustion?

In the context of combustion appliances, particularly regarding safety and efficiency, using living space air for combustion is generally restricted due to concerns about indoor air quality and the potential for creating negative pressure environments. Combustion appliances require a certain amount of air to function efficiently and safely; if this air is drawn from the living space, it can lead to hazardous situations, such as back-drafting or drawing in harmful gases.

The correct understanding is that living space air should not be used for combustion purposes because it can compromise air quality within the home and create risks associated with combustion exhaust. In many scenarios, combustion appliances are required to have a dedicated air supply from outside the building or be vented properly to ensure that combustion occurs safely without depleting the oxygen needed for occupants.

Therefore, the assertion that living space air can be used for combustion is incorrect, as doing so would violate safety standards and protocols meant to protect inhabitants from the risks associated with improper combustion.