FIRE EXTINGUISHERS when full are under pressure and may explode when combined with other materials. As of July 1, 2018, Fire Extinguishers CAN be brought to a Houshold Hazardous Waste collection event for safe and proper disposal. An alternative is to discharge the tank in a safe location, at which point it has been depressurized and can be thrown away as trash if it is plastic, or recycled as scrap metal at the Town's Transfer Station if it is a metal extinguisher.
CARBON MONOXIDE DETECTORS do not contain radioactive material, so you can treat them as you would photoelectric smoke detectors. Check with the manufacturer to see if they have a take-back program. If they do not, remove the battery from your carbon monoxide detector and throw it in the trash.