A1: Different factors that cause hot air:
Your thermostat may be adjusted wrong if your heater sparks chilly air instead of hot.
One of the most common causes of a heater blowing chilly air is a clogged filter.
When air filters are clean, they give your home clean, fresh air. On the other hand, a dirty air filter can cause a heater to vent chilly air.
It's possible that if a furnace only blows chilly air, the heater has overheated.