Combustion Appliance Zone Depressurization Testing (CAZ)

Understanding CAZ Testing

Combustion Appliance Zone Depressurization Testing, commonly referred to as CAZ testing, is a critical assessment process for homes and buildings that utilize atmospheric non-sealed combustion appliances, such as gas water heaters, furnaces, and boilers. The primary goal of CAZ testing is to ensure these appliances can operate safely and efficiently under the worst-case scenario of depressurization.

Why is CAZ Testing Important?

Non-sealed combustion appliances rely on the proper drafting of combustion gases to function safely. If the zone becomes depressurized—due to factors like exhaust fans or tight building envelopes—the appliance may not vent exhaust gases effectively. This can lead to dangerous situations, such as back drafting, where harmful combustion gases re-enter the living space.

The Testing Process

During a CAZ test, a qualified technician will simulate worst-case depressurization conditions. This involves:

1. Measuring Air Pressure: The technician measures the air pressure in the combustion appliance zone to assess how it reacts under depressurization.
2. Testing for Drafting Issues: The technician checks whether the appliance can still draft correctly when the zone is under negative pressure.
3. Identifying Safety Hazards: Any signs of back drafting or improper venting are carefully documented, and recommendations are provided to address any identified issues.