| Answer | Crossword Clue |
|---|---|
| DUCT | Heating system part |
| BOILER | Part of an old heating system |
| BOILER | Heating system component |
| DUCT | Heating system conduit |
| STEAM | A heating system. |
| HUMIDIFIER | Heating system attachment. |
| VENTILATOR | Heating system device. |
| DUCT | Heating system vent |
| DUCTS | Heating system network |
| TRANE | Heating system brand that's "hard to stop" |
