I have a vented gas log for 2 years with no problem. But this year,
it start making roaring sound after it been lighted for about 15-20
minutes. It sounds like the gas rushing and it lasts for 15-20
seconds or so; than it stops for a 10 or so minutes and starts up
again for 15 20 second. I opened the vent/damper all the way but it
still make the roaring sound. Other than the sound, everything seem
to work. Any suggestions will be appricated.