Here are some examples where defects have been found.

corroded supply heating duct
corroded supply heating duct

compromised corroded supply heating duct

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non-insulated ducting in attic
non-insulated ducting in attic

ducting in non-conditioned spaces needs to be insulated and properly secured

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reversed polarity
reversed polarity

The electrical tester shows that the outlet is wired with the hot and neutral wires reversed.

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corroded supply heating duct
corroded supply heating duct

compromised corroded supply heating duct

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