Have you installed a carbon monoxide detector? This lethal gas is odorless!
Is all charcoal-burning equipment used outdoors only? If used indoors, it may result in lethal carbon monoxide levels.
Do you start gas lawnmowers outside of the garage area?
Are all cars turned off immediately upon entering the garage?
Do you have your chimney cleaned periodically to reduce carbon monoxide risk?
Do you have a qualified technician check all central and room heating appliances annually?
Are you careful to never use the gas range or oven for home heating?
Is the area around a gas or kerosene space heater well ventilated?