The answer to 'boiler blowing cold air' is that there are several common causes, including a malfunctioning thermostat, low water pressure, or a problem with the boiler's heating element or controls. This can result in the boiler producing little to no heat, leading to cold air being blown through the vents.
Some common symptoms include the boiler running continuously but not heating the home, lukewarm or cold water from taps, and the boiler's pilot light going out. Solutions may involve adjusting the thermostat, checking the water pressure, or troubleshooting and repairing the boiler's internal components. For most homeowners, it's best to call a professional HVAC technician to diagnose and repair the issue, as boiler maintenance and repairs can be complex and dangerous if not handled properly.