Homeowner Safety Guide
A gas smell around the furnace, gas line, or utility room is a safety situation first. Do not cycle the furnace, light anything, or keep looking for a repair clue. Get away from the smell and use the right emergency or gas-utility path.
If the smell is strong, spreading, or clearly smells like natural gas, leave the area and contact the gas utility or emergency services from a safe location. Do not keep switching the thermostat, resetting power, or opening furnace panels to see what happens next.
Avoid lighting flames, using switches near the smell, or running the furnace again to confirm the symptom. The useful homeowner detail is where the smell was strongest, when it started, and whether the heat tried to run before the smell showed up.
After the gas utility or emergency path says the immediate gas concern is safe, a heating diagnostic can look at the furnace no-heat symptom, ignition behavior, airflow, thermostat call, and shutdown pattern. For normal no-heat symptoms without an active gas smell, start with the $95 Springfield Diagnostic. Nearby towns may cost more.
Read the furnace no-heat guide