I have a small tank off the shed (5000lt) with a fire pump always connected. Though all that only counts If I was at the house at the time of a fire event. though I think it could just burn for hrs and the solid cement block room would contain the fire. Would be a big mess when you opened the door though

Hmmm your points about lifepo4 ventilation and power electronics have me thinking Weber. My situation gets complex with a enclosure within a room that is some times vented and some times sealed (depending on refrigeration requirements). Though there is a separation shelf between the two battery and power electronics at times do share the same rooms volume of air that's sealed.
I wonder if there is some room volume or air exchange numbers that could come into play in the future rule to prevent the flammable air/fuel ratio.I have experienced the same (candy smelling solvent) odors after placing lifep04 cells in sealed boxes for a while then opening the lid. Though unsure if it has reached a point air/fuel ratio to trigger a flame from a spark. Though I haven't smelt it in my small power room. Perhaps the night time fan ventilation is enough to overcome it.
Perhaps I need to program my room ventilation timer to come on at a few intervals pr day to exchange the air...though that won't help with coinciding with a dramatic cell solvent venting event. So many possibility's.
Kurt