The answer to 'why is my humidifier blowing hot air' is that your humidifier may be malfunctioning or not working properly. This can happen if the humidifier is set to the wrong mode, has a faulty heating element, or has a problem with the internal thermostat. Hot air blowing from the humidifier can indicate that the unit is stuck in 'heating' mode and not properly regulating the air temperature and moisture output.
To troubleshoot, first check the humidifier's settings to ensure it is set to the correct mode for your needs. If the settings seem correct, the issue may be with a malfunctioning component inside the unit. In this case, it's best to call in a professional HVAC technician to inspect and repair the humidifier, as attempting DIY repairs could be unsafe.