@Alexandra313
From what I know, most hotels don't provide any kind of compensation if a fire alarm goes off (regardless of real fire or false alarm) in the middle of the night and guests have to evacuate. I've heard that if the hotel feels bad enough and the level of complaints for guests is significant enough, they might offer free meals (breakfast) or pass out drink coupons but I heard that's about it. If Airbnb does not consider this as meeting the "extenuating circumstances" requirement, why should the host? It's not the host's fault and the host has no control over situations like this. This is what "travel insurance" is for.
If it were me and I felt compelled to offer something, I'd say 30~50% of one night as just something to make up for the inconvenience, and nothing more.