Upon arrival, Rick had the furnace already in heating mode to recreate specific situation where strange scent is detected. Upon opening the basment door and taking a step inside, there was a distinct scent change but it smelled more like laundry scents rather than burning plastic. Scent was vaguely detectable near furnace and water heater. Unable to pinpoint scent. While on site, used combustiin analyzer to test first floor vent, basment vent at bottom of stairs, and areas surround furnace for any Carbon Monoxide. 0PPM CO det3cted during and testing. Inspected blower motor, blower compartment, inducer motor, and combustion compartment for anything that could create a burning or strange chemical smell. No issues were found during inspections and testing. Suspect that the scent is something to do with the laundry area being near the basment steps and furnace. If it has not been done recently or checked recently, recommend having the dryer vent checked and/or cleaned to ensure dryer vent