I’ve had two CO events due leaking exhaust systems, even with the heater off gasses can make it into the Cabin. I had the LAME disconnect the scat hose between the exhaust muff and Cabin heat inlet and vent the hot air overboard. Trust me, you’re way better off rugging up in sensible clothing. Not nasty synthetic materials like nylon, but material to provide best fire survival properties and gloves, scarf etc.