The view angle is more wide angle than in height, it depends on the distance the camera is from the fan, the closer it is than it won't catch the fan blades. The Canary Has alert settings for motion (Normal, Medium, High). I would keep it on Normal and you should be alright. I personally like the air quality monitor which also has alert settings.
The website should have the full camera specs including viewing.
The only downfall about canary is that it doesn't have a memory card slot so to save videos for viewing later you'll need to pay $100/year.
Anyway, those are my thoughts.