Hi, There:
I have an aged gas heating system which recently start too slow, it takes about 2-3 times to start comparing to before and sometime it will have weird sound. Can any one tell me what is happen?
Thanks

It is most likely full of dirt. You need to have a professional check it out because a blockage can send carbon monoxide throughout the house killing everyone in it. I hate to see that happen because it is preventable. Don't run it until you get it checked if at all possible and keep windows cracked until then to get fresh air in. You are supposed to have a fresh air supply to furnace, but you also need it in the house. I am in Florida and it's hard to imagine people still using heat in the spring where it's 90 degrees here.