这点事情还镇不住？

Under XX state law, the landlord is required to provide habitable unit for the tenants.  However, these issues do not affect habitability.  

First, CO monitor has expiration date on the unit, it would be changed only 30/60/90 days before that date, not earlier.  

Second, air filter shall be changed only when it is dirty.  If there is evidence showing the filter was dirty when the tenant moved in, the landlord should change it.  Otherwise, tell the tenant the filter was clean at move-in and any dirt on it was caused by him.   In the future, this item should be on the move-in check-list.  Some commercial apartment leases list changes of items that are responsible by the tenant, such as light bulbs, air filters etc. 

Third, there is no definitive evidence to link vent cleaning to improvement of air quality.  (Google vent cleaning necessary?) The tenant is welcomed to do the vent cleaning at his own expense if he feels the need.  

However, dryer duct should be cleaned every year to eliminate fire hazard.