Retrotec DucTester 341 - Manual (Page 9)

Page 9 of 83
©Retrotec Inc. 2014

Air sealing duct work may change the pressure balance in a house and cause back drafting
where it did not occur before. For example, a return leaking to outdoors may have pressurized a
house but when corrected, leaky supplies may reverse that and cause depressurization which
could result in back drafting hot water heaters, furnaces or fireplaces.

Be aware of all possible sources of combustion. Ensure any appliances do not turn on during the
test. Turn off power to the appliance, or set the appliance to the "Pilot" setting. It is possible
for flames to be sucked out of a combustion air inlet (flame rollout) during a test, which is a fire
hazard and can result in high carbon monoxide levels.

If combustion safety problems are found, tenants and building owners should be notified
immediately and steps taken to correct the problem (including notifying a professional heating
contractor if basic remedial actions are not available). Remember, the presence of elevated
levels of carbon monoxide in ambient building air or in combustion products is a potentially life
threatening situation. Air sealing work should not be undertaken until existing combustion
safety problems are resolved, or unless air sealing is itself being used as a remedial action.