If you are wondering where your humidifier is, it is normally hanging from your duct work right near your furnace. You can change the pads yourself or call professionals, if you are nervous or just do not want to do it. The pads can be bought at hardware stores, off the internet, or even from Flame Furnace. If you decided to change your pad yourself, remember to turn the water off! Follow the copper water line until it meets with a bigger water line, where you will find a shut off. If you leave the water line running, there could be a huge mess!
Next time you are enjoying the humidified air that your humidifier provides you, remember that you do need to take care of it to avoid many serious problems.