The answer to 'boiler blowing cold air' is that there are several common causes, including a faulty thermostat, low water pressure, or a problem with the boiler's heating element. Symptoms may include the boiler running but not heating the water, or the water not getting hot enough.
Some potential solutions include checking the thermostat settings, ensuring the water pressure is within the recommended range, and inspecting the heating element for any damage or wear. However, if you're not comfortable troubleshooting the boiler yourself, it's best to call a professional HVAC technician to diagnose and repair the issue.