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Methods Used to Test Duct After Assembly
NOTE: The mentioned leakage tests are not specific to the listing(s) requirements of the system
being tested. Local codes and regulations should be consulted before final inspection. In absence
of local codes and regulations, refer to the latest edition of the International Mechanical Code (IMC)
Chapter 5, Exhaust Systems for inspection and testing requirements.
Method 1 – Light Test per IMC 506.3.2.5
Prior to the concealment of any portion of a duct system, a leakage test shall be performed. Ducts shall be
considered to be concealed where installed in shafts or covered by coatings or wraps that prevent the
ductwork from being visually inspected on all sides. The permit holder shall be responsible to provide the
necessary equipment and perform the duct leakage test. A light test shall be performed to determine that
all welded and brazed joints are liquid tight.
A light test shall be performed by passing a lamp having a power rating of not less than 100 watts through
the entire section of ductwork to be tested. The lamp shall be open so as to emit light equally in all
directions perpendicular to the duct walls. A test shall be performed for entire duct system, including the
hood-to-duct connection. The ductwork shall be permitted to be tested in sections, provided that every joint
is tested. For listed factory-built grease ducts, this test shall be limited to duct joints assembled in the field
and shall exclude factory welds.
Method 2 – Smoke Test
NOTE: Materials or chemicals used for smoke testing should not be corrosive to stainless steel. Smoke
bombs containing chlorine or chlorinated chemicals shall not be used. Consult the factory if there are any
questions regarding compatibility of smoke bombs and duct.
After the ductwork has been installed allow the listed sealant to cure for a minimum of 24 hours. Smoke
bombs are lit and placed at the bottom of the duct system, natural upwards drafts will pull the smoke to the
top of the duct system. Various length duct runs may require multiple smoke bombs. Once the smoke has
reached the top of the duct run, cap the duct securely. Inspect all joints for leakage.
Method 3 – Pressure Testing per SMACNA’s HVAC Air Duct Leakage
Testing and balancing shall be performed prior to the pressure duct leakage test.
A duct pressure test shall be performed during initial installation by the permit holder or its testing agency
using the appropriate local code testing procedure. This test must be performed as a rough inspection prior
to being covered, concealed, insulated or wrapped before final installation to the exhaust fan, kitchen
exhaust hood, or other equipment. In the absence of any local code testing procedures, use SMACNA’s
HVAC Air Duct Leakage Test Manual for inspection and testing guidelines.
If the duct system is modified or altered, the entire system will require re-testing.
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