If your boiler is making a hissing or humming noise, it may be due to high water pressure levels in the system or rapid boiling of the water inside the boiler. It is important to check the system pressure indicators as soon as possible and adjust the pressure if necessary. If the noise continues, the problem may also be related to the wear of the boiler components. Call a licensed professional to prevent damage and ensure safety. Send a quote to find a reliable specialist quickly.