Retrotec Residential Pressure & Air Leakage - Manual (Page 38)

Page 38 of 75
©Retrotec Inc. 2014
5. Some Tests Require Pressure Gauge Only!
Some pressure measurements can be done with a pressure gauge alone. These tests do not require a Blower
Door be installed.
5.1 Combustion and Safety Tests
Combustion and safety tests are best done first, because serious system problems may prevent any further
testing. Combustion Appliance Zone (CAZ) testing is an important aspect of house testing that can determine if
there are any major safety problems. In some cases, air sealing activities done in conjunction with a Blower
Door test can cause safety problems, as a tighter house is more likely to have depressurization problems (which
can lead to combustion products and/or exhaust air leaking into the house).
Please note that the combustion and safety tests in this document are for general reference only. They should
not take the place of local code requirements or procedures.
Combustion products can be spilled back into the building because of the following:

Poor or improper installation of HVAC equipment

Blocked or partially blocked chimneys, vents, or vent connectors

Damaged heat exchangers

Duct systems leaks

Cold temperatures in the chimney stack do not allow for much draft in the chimney flue

Depressurization in the Combustion Appliance Zone (air sealing can cause hazardous depressurization
conditions from exhaust fans and forced air system imbalances)
5.1.1. CAZ Pressure Measurement
Vented combustion appliances require external venting of combustion by-products for safety reasons. If any
appliances are vented, it is important to determine whether any of the exhaust can back draft (be pulled back
into the house).
Worst Case Depressurization Test
There are a number of combustion tests that can be performed, however the most common, and simplest test is
a Worst Case CAZ test. A Worst Case test looks to see if the combined force of all depressurization devices
(exhaust fans) can create a negative pressure (relative to the outdoors), in an area containing a combustion
appliance. If this situation exists, it's possible that the combustion products, including the very dangerous
carbon monoxide, can be pulled into the house and not be vented outside.
To setup the house for a CAZ test
1. Seal the house by closing all exterior windows and doors
2. Open all interior doors
3. Open all supply and return registers
4. Turn off all combustion appliances
The following devices can create a negative pressure (with respect to the outdoors)

Bath exhaust fans

Range hoods