New to the forum, but I've been running on grease for about 3 years.
Over the past couple of years as I've been heating (about 95-100 degrees F) my grease prior to filtering. Sometimes I've noticed that the grease gives off really noxious fumes. The fumes don't really smell that bad or hurt my nose, but they burn my eyes really bad. I've only noticed the fumes on hot or warm grease. Not on cold grease.
It's not related to my grease as my dad has the same problem and has totally different grease and suppliers. We both do heat our grease prior to filtering.