Hallucination
An answer stating something that is not true, delivered with the same confidence as everything else. For a licensed trade this is a liability question, not a marketing one.
Checkable · the test is below
What it means
These systems generate plausible text. Plausible and true are different properties, and nothing in the output distinguishes them for the reader.
Why it matters for an HVAC company
An invented licence status, an invented 24-hour service, an invented price or a wrong phone number all reach a homeowner as fact. You do not control the output and you may be the last to know.
What would settle it
Run your own business through the engines, read every factual claim, and check each against what is true. Log what is wrong and where the wrong version exists on the web, because it usually does exist somewhere.
A worked example
An engine states a contractor offers free estimates on replacements. They charge $89, refundable against the job. The claim traces to a directory profile filled in by someone else in 2021. Correcting that one profile is the whole fix.
The limit on that
There is no mechanism to make an engine stop saying something. Removing the source it drew on is the only lever, and it is indirect.