What is the Combustion Air Zone (I Can Has CAZ?)

Combustion Air Zone, CAZ

by Erik North on August 1, 2011

What is the Combustible Air Zone? I may start an entire category called ‘Clarifying technical energy audit concepts’.

Another energy auditing acronym, the CAZ is the Combustible Air Zone, which sounds like something out of “Top Gun,” doesn’t it? Well, it’s closer to an invisible shield, and that makes it much cooler.

Combustion Air Zone – I Can Has CAZ?

The CAZ is loosely defined as the area housing your home’s combustion heating appliances (boiler, gas furnace, etc.). This includes the heating system, the air used in combustion and other mechanical systems. The CAZ might be a mechanical room, your entire basement or the entire house (for example, a open walk down basement that connects the basement space to the entire house). The CAZ is occasionally located on the main floor, the garage or the attic.

Combustion Air Zone and Safety

The CAZ is extraordinarily important. It is the portion of your house which your heating system pulls combustion air. It interacts with every other air fed combustion appliance within the combustion air zone (OK, when you think about it, not the cleverest name).

As you can imagine, the CAZ must be tested for safety reasons; for example, testing for natural gas leaks, carbon monoxide, chimney draft strength, combustion spillage and, for the worst case scenario, de-pressurization of the CAZ.

Because combustion appliances can interact with one another, the mechanical ventilation running in the home can de-pressurize the CAZ and suck combustion gases out of the flue pipe.

There are ways to address CAZ problems; move to a sealed combustion system (one where the air intake and exhaust are both vented to the outside), adding a direct air supply (basically a line feeding fresh outside air into the heating system), expanding the CAZ if possible or reducing the depressurization again if possible.

In any case, testing the CAZ gives me incredible insight into the combustion process of your home’s heating appliances and helps avoid serious problems.

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