Yes there are requirements/ restrictions on the placement of smoke detectors.
I'm at home and my book is at the office so I may not be exact, but it says:
on ceilings do not mount closer that 12" of wall or near a vent,
when mounted on the wall, mount within 12" but not closer than 6" of ceiling.

Mounting them to close to a vent or fan MAY cause a smoke detector to become to sensitive (false alarm) also should not be mounted outside of bathroom.

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Rick Cantrell
Columbus GA