My 15 yr old Trane XE 80 just is making this minor burning smell, but it only happens every couple of hours or so. I only notice this odor around the vents and it's not very strong, but smells like burning hair and/or insects. I watch it kick on and look & listen for any anomalies, but all sounds and looks fine - Nice blue flame. This is not much to go on, but any advice would be appreciated. Thanks, Eric