Does your gas furnace blower continue blowing and blowing and does not turn off? There are a few reasons this could be happening.
Many theromostats have a “fan continuous” setting which, if enabled, would explain why the blower would not turn off. So change the setting off of fan continuous if this is the case and turn it to the “automatic” setting.
If the setting is not the cause of the blower staying on the problem is likely a faulty fan limit control switch and this will have to be replaced. We strongly suggest you consult your heating expert for this repair.