Crack a window open and let some oxygen into the room. Also consider a humidifier. Heaters dry out the moisture in the room which dries up the mucus in your body. That’s what causes the sickness and dry coughing. It’s not as cold where I live as it is in Canada but we haven’t used the heater for more than 30 minutes at a time and we open up the windows daily. No one in my home got sick this year and we have an elderly living with us.