I am almost 100% sure that the Branch Circuit Overcurrent Device may also serve as the Disconnecting Means (Motor of 1/8 HP max. in a fixed location...)
Heck, if the Blower Assembly is Cord and Plug connected, the Disconnecting Means could be done by Unplugging the Cord from the Receptacle.
The above Should meet minimal compliance, per 2008 NEC - or more accurately in Californ-ieee-yaaa, the 2010 CEC (Title 24, Part 3: Californ-iee-yaa Electrical Code).
IIRC, Motors of 2.0 HP and less would require some type of Local Disconnecting means - i.e.: General Use Toggle Switch, Motor Rated Switch ("Manual Starters"), EXO type Safety Switch, etc.
Personal input:
All the Roof Mounted Exhaust Fans I have seen/installed/fixed/serviced, or inserted as a Block on Electrical Plans [denoted and specified after inserting the appropriate Block, which looks like " \O\ " ... helps if you are drunk ;)]
have / had a Snap Switch mounted external to the Assembly, either directly to it, or within 5 Feet of the Assembly.
Not that this is the only way to achieve Compliance to whatever Code(s) will be applicable to the Equipment, only this is the most prevailing Disconnecting Means method I am used to.
-- Scott (EE)
