Fireplaces, Heating Stoves, Flues and Chimneys - Gas smell from fireplace

Had a strong gas smell in my house a few days ago. Gas company came out and checked, said water heater needs to be replaced and fireplace cleaned. I did both and had the gas fireplace going tonight. After a while there was a strong scent of gas mainly in the furnace room. I believe the furnace then moved the smell through the ducts in the house. Fireplace and furnaxce are in different rooms, why would the scent be so strong in the furnace room? Are there any home gas detection alarms I can get at a hardware store? Who would I call to repair the problem...fireplace guy or HVAC person since the smell is in the furnace room? Much thanks.

Call HVAC guy and have furnace inspected, as it should be annually. If you have checked out all systems, then this is the last. Annual inspections and maintainence of heating/cooling systems is important as well as chimney. Make sure all heating appliances are properly vented.